IV B.Tech. I Sem (R13) ECE : Embedded Systems : UNIT -1 Web viewstepper motor controllers for a robotic system. Motor control systems : accurate control of speed and position of dc

IV B.Tech. I Sem (R13) ECE : Embedded Systems : UNIT -1 1

UNIT – 1

1. Embedded Systems – Introduction (Definition, Applications and Classification) - 1

2. Elements of Embedded systems ----------------------------------------------------------- 5

3. RISC Vs CISC ----------------------------------------------------------------------------------- 84. Von-Neumann & Harvard Architecture ------------------------------------------------- 95. Memory mapped I/O and Isolated I/O ------------------------------------------------

106. Little-Endian and Big-Endian ---------------------------------------------------------------

117. Low Power RISC- MSP 430 : Introduction & Variants of MSP 430 family ----------------

128. MSP430F2013 - Block diagram & features --------------------------------------------------------

189. Memory map of MSP430 ------------------------------------------------------------------------------

2010. MSP430 –CPU architecture & registers ------------------------------------------------------------

2311. Addressing modes of MSP430 -----------------------------------------------------------------------

2812. Instruction formats & Instruction Timings of MSP430 ---------------------------------------

31 13. Instruction set of MSP430 ----------------------------------------------------------------------------

3314. Sample Embedded system on MSP430 ------------------------------------------------------------

39

1. EMBEDDED SYSTEMS - INTRODUCTION

1.1. Definition :• An embedded system is an electronic/electro-mechanical system designed to

perform a specific function and is combination of both hardware and firmware (software). The program instructions written for embedded systems are referred to as firmware, and are stored in Read-Only-Memory or Flash memory.

• Every ES is unique, and the hardware as well as software is highly specialized to the application domain. Embedded systems are designed to do some specific task, rather than be a general purpose computer for multiple tasks.

1.2 . Characteristics of Embedded SystemUnlike general purpose computing system, embedded systems have certain specific characteristics. These characteristics are unique to each embedded system.

1. Application and Domain Specific2. Reactive and Real Time3. Operates in harsh environments4. Distributed5. Small size and weight6. Power concerns

1.3. Quality attributes of Embedded Systems

VISVODAYA TECHNICAL ACADEMY:: KAVALI


(a)Operational Quality Attributes : These are related to the embedded system when it is in the operational mode (or) online mode.

1. Response2. Throughput3. Reliability4. Maintainability5. Security6. Safety

(b)Non-Operational Quality Attributes: These attributes are addressed for the product.

1. Testability and Debug ability2. Evolvability – can be modified to take advantage of new technology3. Portability4. Time to prototype and market5. Per Unit & Total cost

1.4. Application of Embedded Systems

The embedded systems are used in various domains. Within the domain itself, according to the application, they may have different functionalities. Each embedded system is designed to serve the purpose of any one or a combination of the following tasks:

Purpose of Embedded System Data Collection/Storage/Representation Data communication Data signal processing Monitoring Control Application specific user interface

The different applications/Examples of Embedded systems are given below

1. Consumer Electronics: Camcorders, Cameras.2. Household appliances: Digital TVs, DVD players, Set top boxes, Washing

machine, Refrigerator.

3. Automotive industry: Anti-lock breaking system (ABS), engine control, automatic

navigation system, engine control4. Home automation & security systems: Air conditioners, sprinklers, fire

alarms, closed circuit television cameras, home security system

5. Telecom: Cellular phones, telephone switches, handset multimedia applications

6. Computer peripherals: Printers, scanners, fax machines7. Computer networking systems: Network routers, switches, hubs, firewalls8. Healthcare: EEG, ECG machines.9. Banking & Retail: Automatic teller machines(ATM), currency counters,

point of sales.10.Card Readers: Barcode, smart card readers.



11.Measurements & Instrumentation : Logic Analyzers, Spectrum analyzers, PLC systems,

Electronic data acquisition and supervisory control system, industrial process controller, digital meters

12.Missiles and Satellites : Defense, Aerospace, Communication, tracking system

13.Robotics : stepper motor controllers for a robotic system14.Motor control systems : accurate control of speed and position of dc motor15.Entertainment systems : video games, music system16.Signal & Image processing : speech processing, pattern recognizer, video

processing

1.5. General Purpose Computing System Vs Embedded System :

General Purpose Computing system Embedded system

It is combination of generic hardware and a general purpose OS for executing a variety of applications.

It is combination of special purpose hardware and embedded OS for executing specific set of applications

It contains generalpurpose operating system

It may or may not contain an operating system for functioning.

Applications are alterable (programmable)by the user.

Applications are non-alterableby the user.

Performance is the key deciding factor in the selection of the system. Always ‘faster is better’.

Application specific Requirements (performance, power requirements, memory usage, size, design and manufacturing cost, etc) are the key deciding factors.

Less tailored towards reduced operating power requirements, options for different levels of power management.

Highly tailored to take the advantage of the power saving modes supported by the hardware and the operating system.

Response requirements are not time-critical.

For certain category of embedded systems like mission critical systems, the response time requirement is highly critical.

Need not be deterministic in execution behavior.

Execution behavior is deterministic for certain types of Embedded systems like ‘Hard Real Time’ systems.

1.6. Classification of Embedded Systems

The classification of embedded system is based on following criteria's:(a) On generation(b) On complexity & performance



(c) On deterministic behaviour(d) On triggering

(a)Classification based on generation

1. First generation(1G): Built around 8-bit microprocessors like 8085, Z80 and 4-bit

microcontrollers. Simple in hardware circuit with firmware developed in Assembly code. Examples: Digital telephone keypads, stepper motor control units

2. Second generation(2G): Built around 16-bit μp and 8-bit μc. They are more complex & powerful than 1G μp & μc. Examples: Data Acquisition system (DAS), Supervisory Control and Data

Acquisition systems (SCADA)

3. Third generation(3G): Built around 32-bit μp & 16-bit μc. A new concept of application and domain specific processors / controllers

like Digital Signal Processors(DSPs), Application Specific Integrated Circuits(ASICs).

Examples: Robotics, Media, Industrial process control, networking, etc.

4. Fourth generation: Built around 64-bit μp & 32-bit μc. The concept of System on Chips (SoC), reconfigurable processors, multi-

core processors High performance, tight integration, miniaturization, and very powerful. Examples: Smart Phones, Mobile Internet Devices

(b)Classification based on Complexity and performance

1. Small-scale: Simple applications where the performance requirements are not time-

critical. Built around low performance and low cost 8 or 16 bit μp/μc. Example: an electronic toy

2. Medium-scale: Slightly complex in hardware and firmware requirement. Built around medium performance and low cost 16 or 32 bit μp/μc. Usually contain embedded operating system ( either general purpose /

RTOS) for functioning Examples: Industrial machines.

3. Large-scale: Highly complex hardware & firmware. Built around 32 or 64 bit RISC μp/μc or PLDs or SoC or multi-core

processors. Response is time-critical. Examples: Mission critical applications.



(c)Classification based on deterministic behavior

This classification is applicable for “Real Time” systems. The task execution behavior for an embedded system may be

deterministic or non-deterministic. Based on execution behavior Real Time embedded systems are divided

into Hard and Soft.

(d)Classification based on triggering

Embedded systems which are “Reactive” in nature can be based on triggering.

Reactive systems can be Event triggered (or) Time triggered

2. ELEMENTS OF EMBEDDED SYSTEM :

Embedded systems are basically designed to regulate a physical variable (or) to manipulate the state of some devices by sending some signals to the actuators or devices connected to the output ports of the system, in response to the input signals provided by the end users or sensors which are connected to the input ports. Hence the embedded systems can be viewed as a reactive system. The control is achieved by processing the information coming from the sensors and user interfaces and controlling some actuators that regulate the physical variable.

Common user interface input devices : Keyboards, push button, switches, etc.Common user interface output devices : LEDs, LCD, Buzzers…etc

Note that it is not necessary that all ES should incorporate these I/O user interfaces. It depends on the type of application in which the ES is designed. For ex., if the ES is designed for any handheld application such as a mobile handset, the system should contain user interfaces like keyboard, display unit, speakers, microphone etc. Some Embedded Systems do not require any manual intervention for their operation. They automatically sense the variations in the input parameters using sensors which are connected to the input port, and the processor performs some pre-defined operations with the help of firmware embedded in the system and sends some actuating signals to the actuators connected to the output port of the Embedded system.

Sensors connected to the input port to sense/detect the changes in the input variables

converts input variables into electrical signals for any measurements/ control purpose

Actuators connected at the output port converts electrical signals into corresponding physical action .



Figure .1 : Elements of an Embedded System

The memory of the system is responsible for holding the control algorithm and other important configuration details. Memory for implementing the code may be present on the processor or may be implemented as a separate chip interfacing the processor. In a controller based embedded system, the controller may contain internal memory for storing code.

Embedded systems are domain and application specific and are built around a central core. The core of the embedded system falls into any of the following categories:

1. General purpose and Domain Specific Processors2. Microprocessors3. Microcontrollers4. Digital Signal Processors5. Application Specific Integrated Circuits (ASIC)6. Complex Programmable Logic Devices (CPLD’s)7. Field Programmable Gate Arrays (FPGA)8. Commercial off-the-shelf components (COTS)

Almost 80% of the embedded systems are processor/ controller based. The processor may be microprocessor or a microcontroller or digital signal processor, depending on the domain and application. Most of the ES in industrial control and monitoring applications make use of the commonly available microprocessors and microcontrollers whereas domains which require signal processing such as speech coding, speech recognition..etc make use of special kind of digital signal processors supplied by manufacturers like Analog Devices, Texas Instruments,..etc

Microprocessors A microprocessor is a silicon chip representing a central processing unit (CPU),

which is capable of performing arithmetic and logic operations according to a pre-defined set of instructions.

In general, the CPU contains ALU, Control Unit and working registers. A microprocessor is a dependent unit and it requires the combination of other

hardware like memory, timers, interrupt controller and I/O ports, etc. for proper functioning.

Microprocessors are used in general purpose applications.

Microcontrollers



A microcontroller is an integrated chip that contains CPU, data and program memory ( RAM and ROM), special and general purpose registers, Timers, Interrupt control unit and dedicated I/O ports.

Since a microcontroller contains all the necessary functional blocks for independent working, they found greater place in embedded domain.

Microcontrollers are application oriented and used in domain-specific applications.

Digital Signal Processors DSPs are powerful special purpose 8/16/32 bit processors, designed specifically

to meet the computational demands and power constraints of today’s embedded audio, video and communication applications.

DSP are 2 to 3 times faster than general purpose microprocessors in signal processing applications. This is because of the architectural difference between DSP and general purpose microprocessors.

DSPs implement algorithms in hardware which speeds up the execution whereas general purpose processor implement the algorithm in software and the speed of execution depends primarily on the clock for the processors.

DSP performs large amount of real-time calculations like FFT(Fast Fourier Transform), DFT(Discrete Fourier Transform), Convolution, SOP(Sum of Products) calculation etc.

Audio video signal processing, telecommunication and multimedia applications are typical examples where DSPs are employed.

Application Specific Integrated Circuit (ASIC)

ASIC is a microchip designed to perform a specific or unique application. It integrates several functions into a single chip there by reduces the system

development cost.

CPLD and FPGA

The PLDs consists of a large no. of programmable gates on a VLSI chip With programmable logic devices like CPLDs and FPGAs, the designs can be

quickly simulated, tested and programmed into devices and immediately tested in live circuits.

During the design phase, the circuit can be changed by programming the device to get the desired outputs, because these devices are based on re-writable memory technology.

These devices are used in Network routers, DSL modem, an automotive navigation system

Commercial off-the-shelf components (COTS)

Commercial off-the-shelf (COTS) product is one which is used ‘as-is’ COTS products are designed in such a way to provide easy integration with

existing system components. The COTS component itself may be developed around a general purpose or

domain specific processor or ASIC or PLDs. The example for COTS product is TCP/IP plug-in module



3. RISC Vs CISC :

RISC and CISC are the two common Instruction Set Architectures (ISA) available for processor design.

RISC (Reduced Instruction Set Computer))

CISC (Complex Instruction Set Computer)

1 Supports lesser number of instructions.

Supports greater number of instructions.

2Supports few addressing modes for memory access and data transfer instructions.

Supports many addressing modes for memory access and data transfer instructions.

3 Single, fixed length instructions Variable length instructions

4 Instructions take fixed amounts of time for execution

Instructions take varying amounts of time for execution

5 Instruction pipelining works effectively and increases the execution speed.

Instruction pipelining concept is not effectively works as different sizes and different execution times of instructions.

6 Orthogonal instruction set (allows each instruction to operate on any register and use any addressing

Non-orthogonal set (all instructions are not allowed to operate on any register and use any addressing mode.



mode.)

7 Less silicon usage and decoding logic is not complex.

More silicon usage since more additional decoder logic is required to implement the complex instruction decoding.

8 Because of the simple instructions, the design of compiler is easy.

Because of large amount of different and complex instructions, the design of compiler is complex.

9 A larger number of registers are available.

Limited no. of general purpose registers

10

Operations are performed on registers only.Memory operations are load and store only.

Operations are performed either on registers or memory depending on instruction.

11 With Harvard Architecture. Can be Harvard or Von-Neumann

Architecture.

12

Programmer needs to write more code to execute a task since instructions are simpler ones. ( large code sizes)

The programmer can achieve the desired functionality with a single instruction. (small code sizes)

4. HARVARD ARCHITECTURE Vs VON-NEUMANN ARCHITECTURE :

Architectures used for processor design are Harvard or Von- Neumann.

Harvard architecture Von-Neumann architecture

It has separate buses for instruction as well as data fetching. This means that, the data memory and program memory are separated.

It shares single common bus for instruction and data fetching. This means that only one set of addresses covers both data memory and program memory. The memory map shows the addresses at which each type of memory is located.



Easier to pipeline, so high performance can be achieve.

Low performance as compared to Harvardarchitecture

It allows simultaneous access to the program and data memories. For instance, the CPU can read an operand from the data memory at the same time as it reads the next instruction from the program memory.

First fetches the instruction and then fetches the data. The two separate fetches slows down the controller’s operation. Because several memory cycles are needed to extract a full instruction from memory, this architecture is intrinsically less efficient.

Since data memory and program memory are stored physically in different locations, no chances exist for accidental corruption of program memory

Accidental corruption of program memory may occur if data memory and program memory are stored physically in the same chip.

A problem with the Harvard architecture is that constant data (often lookup tables) must be stored in the program memory because it is nonvolatile. This means that constants cannot be read in the same way as volatile values from the data memory. Special “table read” instructions must therefore be provided or part of the program memory is mapped into data memory

The system is simpler and there is no difference between access to constant and variable data.

Separate decoding logic is required, because separate buses and control signals are used for accessing data memory and program memory

No additional logic is required because, Same bus and control signals are used for accessing for both data memory and program memory.

Comparatively high cost Low cost

5. MEMORY MAPPED I/O & I/O MAPPED I/O :

Memory mapped I/O Port mapped I/O

1

I/O devices are mapped into the system

I/O devices are mapped into a separate address space. i.e., there is separate address space for memory



memory map. i.e Common address space for memory and I/O ports (The I/O ports are viewed as memory locations and are addressed likewise)

and I/O ports.

2The control signals used for memory operation and I/O operation are same.M/IO = 1 for both Memory and I/O operations

Different control signals are used for memory and I/O operations.M/IO =1 for memory operationM/IO =0 for I/O operation

3 All instruction which can access memory can be used to access I/O ports.

Less no. of instructions are for I/O access. ( only IN and OUT instructions)

4 The data can be moved from any register to I/O port and vice-versa.

The data transfer takes place between Accumulator and I/O port only

5

The arithmetic, logic and bit manipulation instructions which are available for data in memory can also be used for I/O operations. Hence the processor can directly manipulate data from I/O port.

No instructions are available for direct manipulation of I/O data. First the processor reads data from I/O port and then manipulates.

6 Large number of I/O devices can be interfaced

Less no. of I/O devices can be interfaced

7Full address space can’t be used for addressing Memory, because some locations are allotted for I/O ports.

Full address space can be used for addressing Memory, because I/O locations are separated from memory.

8The entire address bus must be fully decoded for every device, which increases the cost

Less logic is needed to decode a discrete address and therefore less cost

5. LITTLE-ENDIAN & BIG-ENDIAN PROCESSORS

Endianness specifies the order which the data is stored in the memory by processor operations in a multi byte system.

Little-endian means lower order data byte is stored in memory at the lowest address and the higher order data byte at the highest address.

For ex., 4 byte long integer Byte3, Byte2, Byte1, Byte0 will be stored in memory as follows:

Base address 2000 H

Base address+1 2001H

Base address+2 2002 H




Big-endian means the higher order data byte is stored in memory at the lowest and the lower order data byte at the highest address.

For ex., 4 byte long integer Byte3, Byte2, Byte1, Byte0 will be stored in memory as follows:

Base address 2000 H




7. INTRODUCTION TO MSP430 MICROCONTROLLERS:

Introduction :

1. The MSP430 microcontroller from Texas Instruments (TI) is a 16-bit RISC based Mixed Signal Processor with Von-Neumann architecture, designed for low power and portable applications.

2. The architecture supports different low-power modes, and it is optimized to achieve extended battery life in portable measurement applications. The digitally controlled oscillator (DCO) allows wake-up from low-power modes to active mode in less than 1 micro second.

3. It is extremely easy to put the device into a low-power mode. No special instruction is needed: The mode is controlled by bits in the status register. The MSP430 is awakened by an interrupt and returns automatically to its low-power mode after handling the interrupt.

4. The address and data buses are 16-bits wide and the registers in CPU are also 16-bits wide. Hence the registers can be used for either data (or) addresses.



5. Since it has 16-bit address bus, it can address 64KB of memory (RAM/ROM/Flash/Reg). The amount of on-chip memory varies for different families of MSP430.

6. A wide range of peripherals are available, many of which can run autonomously without the CPU for most of the time.

7. Many portable devices include liquid crystal displays, which the MSP430 can drive directly.

8. Some MSP430 devices are classed as application-specific standard products (ASSPs) and contain specialized analog hardware for various types of measurements.

9. The MSP430 family consists of several devices featuring different sets of peripherals targeted for various applications : Internal oscillator, Timer including PWM, WDT, Serial communication interface (USART, I2C, SPI), ADC, DAC, Comparators, Multipliers, Brownout reset circuitry, Op-Amps for signal conditioning, LCD driver, DMA, built-in bootstrap loader (BSL) using UART such as RS232 or USB, JTAG interface.. etc.

MAIN CHARACTERISTICS OF MSP430 MICROCONTROLLER

Although there are variants in devices in the family, a MSP430 microcontroller can be characterized by:

Flash (or) ROM-based low-power MCUs CPU clock : 8/16 MHzOperating voltage : 1.8–3.6 VPower specification overview, as low as:

0.1 μA RAM retention 0.7 μA real-time clock mode peration 160 - 250 µA/MIPS at active operation Fast wake-up from standby mode in less than 1 µs.

Device parameters Flash/ ROM options: 1 KB – 60 KB RAM options: 128 B– 8 KB GPIO options: 14 - 80 pins

Other integrated peripherals: 10/12/16-bit Analogue-to-Digital Converter (ADC); 12-bit dual Digital-to-Analogue Converter (DAC);



Comparator-gated Timers; Watch Dog Timer SPI, I2C, UART Operational Amplifiers (OP Amps) 16×16 multiplier Comparator_A Temp. sensor LCD driver Supply Voltage Supervisor (SVS) Brown out Reset

16 bit RISC CPU: Instructions processing on either bits, bytes or words; Compact core design reduces power consumption and cost; Compiler efficient; 27 core instructions; 7 addressing modes; Extensive vectored-interrupt capability.

MSP430X : There is a new extended version of original MSP430 architecture, called MSP430X, which can address extra memory with other improvements as well.

If CPU is MSP430, it has 16-bit address bus and it can address 64 KB of memory (0x0000 – 0xFFFF)

If the CPU is MSP430X, it has 20-bit address bus and it can address 1 MB of memory. The bottom 64 KB of memory from 0x0000 to 0xFFFF is same way as in the original MSP430. The additional memory from 0x10000 to 0xFFFFF, is available for additional ROM. This allows larger programs and tables to be stored.

VARIANTS OF MSP430 FAMILYMSP430 part numbering:

MSP 430 The letters MSP stand for mixed signal processor, which is a reminder that many practical applications require analog inputs. MSP430 indicates the member of the 430 MCU platforms.

F The letter after MSP430 shows the type of memory.



F : flash memory, C : masked ROM

G (optional)

There is a second letter for ASSPs (Application Specific Standard Products) to show the type of measurement for which they are intended. E : for electricity (Energy meters), W : for water (flow meters), and G : for signals that require gain stage (Medical), provided by Op-Amps.

4

It indicates the generation of the device 1 series : upto 8 MHz, 2 series : upto 16 MHz 3 series : Legacy OTP (one time programmable) 4 series : upto 16 MHz with w/LCD 5 series : upto 25 MHz 6 series : upto 25 MHz with w/LCD

6 Model within generation (Various levels of integration within a series)

19Memory size and peripheral configuration 03 : 128 byes RAM & 1 KB ROM 13 : 128 byes RAM & 2 KB ROM

ITemperature range I : -40 to 85 oC, T : -40 to 105 oC, S : 0 to 50 oC

QZW Package (Ball Grid Array/ Pin Grid Array/ Dual In-line Package)

R (optional)

Tape and Reel T = Small Reel (7 –in) R = Large Reel (11 –in)

MSP430x1xx :

MSP430x1xx Provides a wide range of general-purpose devices from simple versions to complete systems for processing signals. There is a broad selection of peripherals and some include a hardware multiplier, which can be used as a basic digital signal processor.

Flash- or ROM-based low-power MCUs 8 MHz Clock, 1.8–3.6 V operationPower specification overview, as low as:

0.1 μA RAM retention 0.7 μA real-time clock mode 200 μA / MIPS active Features fast wake-up from standby mode in less than 6 µs.

Device parameters Flash/ROM options: 1–60 KB RAM options: 128 B– 2 KB GPIO options: 14/22/48 pins ADC options: Slope, 10 & 12-bit SAR



Other integrated peripherals: 12-bit DAC, up to 2 16-bit timers, WDT, brown-out reset, SVS, USART module (UART, SPI), DMA, 16×16 multiplier, Comparator_A, Temp. sensor

MSP430F2xx :

The MSP430F2xx Series are similar to the '1xx generation, but operate at even lower power, support up to 16 MHz operation, double the speed of earlier devices, while consuming only half the current at the same speed. It has On-chip clock (VLO) that makes it easier to operate without an external crystal. Pull-up or pull-down resistors are provided on the inputs to reduce the number of external components needed. Some come in 14-pin package with PDIP option, which is attractive for anybody who has to build circuits by hand.

Flash- or ROM-based low-power MCUs 16 MHz Clock, 1.8–3.6 V operationPower specification overview, as low as:

0.1 μA RAM retention 0.3 μA standby mode (VLO) 0.7 μA real-time clock mode 220 μA / MIPS active Feature ultra-fast wake-up from standby mode in less than 1 μs

Device parameters Flash/ROM options: 1 KB–60 KB RAM options: 128 B – 8 KB GPIO options: 10/16/24/32/48 pins ADC options: Slope, 10 & 12-bit SAR, 16 & 24-bit Sigma Delta

Other integrated peripherals: operational amplifiers, 12-bit DAC, up to 2 16-bit timers, watchdog timer, brown-out reset, SVS, USI module (I²C, SPI), USCI module, DMA, 16×16 multiplier, Comparator_A+, Temperature sensor

MSP430x3xx :

The MSP430x3xx Series is the oldest generation, designed for portable instrumentation with an embedded LCD controller. This also includes a frequency-locked loop oscillator that can automatically synchronize to a low-speed (32 kHz) crystal. This generation does not support EEPROM memory, only mask ROM and UV- eraseable and one-time programmable EPROM.

UV erasable and One Time Programmable ROM 16 MHz Clock, 2.5 – 5.5 V operationPower specification overview, as low as:


Device parameters: ROM options: 2–32 KB RAM options: 512 B–1 KB



GPIO options: 14/40 pins ADC options: Slope, 14-bit SAR

Other integrated peripherals: LCD controller, multiplier

MSP430x4xx :

MSP430x4xx series can drive LCDs with up to 160 segments. Many of them are ASSPs, but there are general-purpose devices as well. These devices are used for low power metering and medical applications.

Flash- or ROM-based ultra-low-power MCUs 16 MHz Clock, 1.8–3.6 V operationFLL and SVSPower specification overview, as low as:


Device parameters: Flash/ROM options: 4 KB– 60 KB RAM options: 256 B – 8 KB GPIO options: 14/32/48/56/68/72/80 pins ADC options: Slope, 10 & 12-bit SAR, 16-bit Sigma Delta

Other integrated peripherals: 12-bit DAC, Op Amps, RTC, up to two 16-bit timers, watchdog timer, basic timer, brown-out reset, SVS, USART module (UART, SPI), USCI module, LCD Controller, DMA, 16×16 & 32x32 multiplier, Comparator_A, Temp. sensor

MSP430x5xx series :

The MSP430x5xx Series are able to run up to 25 MHz, have up to 512 KB flash memory and up to 66 KB RAM. Includes an innovative power management module for optimal power consumption and integrated USB.

Flash- or ROM-based ultra-low-power MCUs 25 MHz Clock, 1.8–3.6 V operationPower specification overview, as low as:


Device parameters: Flash options: up to 512 KB RAM options: up to 66 KB ADC options: 10 & 12-bit SAR GPIO options: 29/31/47/48/63/67/74/87 pins

Other integrated peripherals: High resolution PWM, 5 V I/O's, USB, backup battery switch, up to 4 16-bit timers, watchdog timer, Real-Time Clock, brown-



out reset, SVS, USCI module, DMA, 32x32 multiplier, Comp B, temperature sensor

MSP430x6xx series

The MSP430x6xx Series are able to run up to 25 MHz, have up to 512 KB flash memory and up to 66 KB RAM. It includes an innovative power management module for optimal power consumption and integrated USB.

Flash- or ROM-based ultra-low-power MCUs 25 MHz Clock, 1.8–3.6 V operationPower specification overview, as low as:


Device parameters: Flash options: up to 512 KB RAM options: up to 66 KB ADC options: 10 & 12-bit SAR GPIO options: 74/90 pins

Other integrated peripherals: USB, LCD, DAC, Comparator_B, DMA, 32x32 multiplier, power management module (BOR, SVS, SVM, LDO), watchdog timer, RTC, Temp sensor

8. BLOCK DIAGRAM OF MSP430 F2013/ F2003 MICROCONTROLLER

The MSP430 microcontroller from Texas Instruments (TI) is a 16-bit RISC based Mixed Signal Processor with Von-Neumann architecture, designed for low power and portable applications.

It is extremely easy to put the device into a low-power mode. No special instruction is needed: The mode is controlled by bits in the status register. The MSP430 is awakened by an interrupt and returns automatically to its low-power mode after handling the interrupt.

The address and data buses are 16-bits wide and the registers in CPU are also 16-bits wide. Hence the registers can be used for either data (or) addresses.



The functional block diagram of the MSP430 F2003/F2013 consists of the following blocks :

On the left is the 16-bit CPU and its supporting hardware, including the clock generator.The emulation, JTAG interface and Spy-Bi-Wire are used to communicate with a desktop computer when downloading a program and for debugging.

The main blocks are linked by the memory address bus (MAB) and memory data bus (MDB).

It has flash memory, 1KB in the F2003 or 2KB in the F2013, and 128 bytes of RAM.

Six blocks are shown for peripheral functions (there are many more in larger devices). Input/output ports, Timer_A, and a watchdog timer, Universal serial interface (USI) and sigma–delta analog-to-digital converter (SD16_A) are particular features of this device.

The brownout protection comes into action if the supply voltage drops to a dangerous level. Most devices include this but not some of the MSP430x1xx family.



There are ground and power supply connections. Ground is labeled VSS and is taken to define 0V. The supply connection is VCC. For many years, the standard for logic was VCC =+5V but most devices now work from lower voltages and a range of 1.8–3.6V is specified for the F2013. The performance of the device depends on VCC. For ex., it is unable to program the flash memory if VCC < 2.2V and the maximum clock frequency of 16MHz is available only if VCC ≥ 3.3V.

The brownout reset circuit detects low supply voltages such as when a supply voltage is applied to (or) removed from the VCC terminal. The brownout reset circuit resets the device by triggering a POR (Power on Reset) signal when power is applied (or) removed. The brownout circuit is used to provide the proper internal reset signal to the device during power ON and power OFF.)

The Watchdog Timer (WDT) module restarts the system on occurrence of a software problem (or) if a selected time interval expires. It is used to detect and recover from computer malfunction.During normal operation, the system regularly restarts the watchdog timer to prevent it from elapsing, or "timing out". If the system fails to restart the watchdog due to a hardware fault or program error,, the timer will elapse and generate a timeout signal. The timeout signal is used to initiate corrective actions like placing the system in a safe state and restoring normal system operation. Remember that the watchdog is active by default and must either be disabled or regularly cleared before it rolls over. The WDT can also be used to generate timely interrupts for an application.

The Supply Voltage Supervisor (SVS) is used to monitor the supply voltage or an external voltage. The SVS can be configured to set a flag or generate a POR reset when the supply voltage or external voltage drops below a user selected threshold.

The SVS features include:• Supply voltage VCC monitoring• Selectable generation of POR• Output of SVS comparator accessible by software• Low-voltage condition latched and accessible by software• 14 selectable threshold levels• External channel to monitor external voltage

9. MEMORY MAP OF MSP430 :

The MSP430 von-Neumann architecture has address space shared with special function registers (SFRs), peripherals, RAM, and Flash/ROM memory. The following shows the memory map of the F2013. Most MSP430 devices have a similar memory map, differing only in the size of the regions for RAM and ROM.



Figure : Memory map of the MSP430F2013

0000 – 000F Special Function Registers (byte access)0010 – 00FF Peripheral registers with Byte access0100 – 01FF Peripheral registers with Word access0200 – xxxx RAM ( upper boundary varies)0C00 – 0FFF Bootstrap loader ( not in F20xx)

1000 – 10FF

Flash Information memory ( available in Flash devices only)

xxxx - FFBF Flash / ROM ( lower boundary varies) FFC0 - FFFF Interrupt & Reset Vector Table

Special function registers : The SFRs are located in the lower 16 bytes of the address space. Some peripheral functions are configured in the SFRs for enabling and signaling interrupts from peripherals. SFRs must be accessed using byte instructions only.

Peripheral registers with byte access and peripheral registers with word access:



Provide the main communication between the CPU and peripherals. Some must be accessed as words and others as bytes. They are grouped in this way to avoid wasting addresses. The address space from 010h to 0FFh is reserved for 8-bit peripheral modules. These modules should be accessed with byte instructions.The address space from 0x0100 to 0x01FF is reserved for 16-bit peripheral modules. These modules should be accessed with word instructions.

Random access memory: Used for variables. RAM always starts at address 0x0200 and the end address of RAM depends on the amount of RAM present on the device. The F2013 has 128 Bytes of RAM.

Bootstrap loader (Flash devices only) : The MSP430 flash devices contain an address space for boot memory, located between addresses 0xC00 through to 0x0FFF. The “bootstrap loader” is located in this memory space, which is an external interface that can be used to program the flash memory in addition to the JTAG. This memory region is not accessible by other applications, so it cannot be overwritten accidentally.

Information memory (Flash devices only) :A 256B block of flash memory that is intended for storage of nonvolatile data. This might include serial numbers to identify equipment—an address for a network, for instance—or variables that should be retained even when power is removed. ( It is like an onboard EEPROM, where variables needed for the next power up can be stored during power down.)For example, a printer might remember the settings from when it was last used and keep a count of the total number of pages printed.

Flash memory may be written one byte or word at a time, but must be erased in segments. The information memory is divided into 2 segments (of 128-bytes each) in 4xx devices, and 4 segments (of 64 bytes each) in 2xx devices. Segment A contains factory calibration data for the DCO in the MSP430F2xx family and is protected by default.

Flash/ROM /Code memory: Holds the program, including the executable code itself and any constant data. The start address of Flash/ROM depends on the amount of Flash/ROM present on the device. The end address for Flash/ROM is 0x0FFFF for devices with less that 60KB of Flash/ROM. The F2013 has 2 KB but the F2003 only 1KB.Flash can be used for both code and data. Word or byte tables can be stored and used in Flash/ROM without the need to copy the tables to RAM before using them. The interrupt vector table is mapped into the upper 16 words of Flash/ROM address space, with the highest priority interrupt vector at the highest Flash/ROM word address (0x0FFFE).

Interrupt and reset vectors :



Used to handle “exceptions,” when normal operation of the processor is interrupted or when the device is reset. This table was smaller and started at 0xFFE0 in earlier devices.

The range of addresses has been extended from 64KB to 1MB in the MSP430X. This means that addresses require 20 bits rather than 16 and the MAB is therefore 20- bits wider. The bottom 64KB of memory from 0x00000 to 0x0FFFF is laid out in exactly the same way as in the original MSP430. The additional memory, from 0x10000 to 0xFFFFF, is available for additional ROM. This permits larger programs and tables to be stored.

The above figure shows - Bits, Bytes, and Words in a Byte-Organized Memory. For all devices, each memory location is formed by 1 data byte. The CPU is capable

of addressing data values either as bytes (8 bits) or words (16 bits). Bytes are located at even or odd addresses. Words are always addressed at an even address, which contain the least

significant byte, followed by the next odd address, which contains the most significant byte.

For 8-bit operations, the data can be accessed from either odd or even addresses, but for 16-bit operations, the data values can only be accessed from even addresses.

For example, if a data word is located at address 0x0200, then the low byte of that data word is located at address 0x0200, and the high byte of that word is located at address 0x0201.

This is called as Little-endian ordering, in which the low-order byte is stored at lower memory address and high-order byte is at the higher address. For example, if a word contains the hexadecimal value 0x1234. Its less significant (low-order) byte is 0x34 and it is stored at lower memory address 0x0200 and the most significant (high-order) byte 0x12 is store at higher memory address 0x0201.



10. CPU ARCHITECTURE & REGISTERS OF MSP430

The central processing unit (CPU) executes the instructions stored in memory. It steps through the instructions in the sequence in which they are stored in memory until it encounters a branch or when an exception occurs (interrupt or reset).

The CPU can run at a maximum clock frequency fMCLK of 16MHz in the MSP430F2xx family and some newer MSP430x4xx devices, and 8MHz in the others. It is built using static logic, which means that there is no minimum frequency of operation: The CPU can be stopped and will retain its state until it is restarted. This is essential for low-power operation to be straightforward.



The CPU features include: 16-bit RISC architecture with 27 instructions and 7 addressing modes. Orthogonal architecture with every instruction usable with every addressing

mode. Full register access including program counter, status registers, and stack

pointer. Single-cycle registers operations Large 16-bit register file reduces fetches to memory. 16-bit address bus allows direct access and branching throughout entire

memory range. 16-bit data bus allows direct manipulation of word-wide arguments. Constant generator provides six most used immediate values and reduces code

size. Word and byte addressing and instruction formats. It can address the complete address range without paging It includes the arithmetic logic unit (ALU), which performs computation, a set of

16 registers designated R0–R15 and the logic needed to decode the instructions and implement them.

Figure : CPU Registers of MSP430

MSP430 CPU registers

The CPU incorporates sixteen 16-bit registers: Four registers (R0, R1, R2 and R3) have dedicated functions; 12 working registers (R4 to R15) for general use.

R0: Program Counter (PC) : The 16-bit Program Counter (PC/R0) points to the next instruction to be fetched

from memory and executed by the CPU. The Program counter is incremented by the number of bytes used by the

instruction (2, 4, or 6 bytes, always even). It is important to remember that the PC is aligned at even addresses, because

the instructions are composed of 1-3 words. Hence the LSB of PC is hard-wired to 0.

R1: Stack Pointer (SP) The stack memory is a memory block where the data is stored in LIFO manner. The Stack Pointer (SP/R1) holds the address of the stack-top. In the MSP430, as in many other processors, the stack is allocated at the top of

the RAM and grows down towards low addresses.



The LSB of of the stack pointer is hardwired to 0 in the MSP430, which guarantees that it always points to valid words. A byte is therefore wasted to preserve the alignment to words if a single byte is placed on the stack.

Operation of the Stack :

The operation of the stack is illustrated in the following figure. The specific addresses are for MSO430F2013 with 128 Bytes of RAM are from 0x0200 to 0x027F. Hence, Before the execution, the initially the value of SP = 0x0280

The purpose of the stack :

It used by subroutine calls to store the program counter value for return at the end of subroutine (RET). When a subroutine is called, the CPU jumps to the subroutine, executes the code there, then returns to the instruction after the call. It must therefore keep track of the contents of the PC before jumping to the subroutine, so that it can return afterward. This is the primary purpose of the stack.

It is used by interrupt - system stores the actual PC value first, then the actual status register content on top of the stack. After servicing the interrupt, the system get the same status as just before the interrupt happened by executing the instruction return from interrupt (RETI).

It can be used by compiler for subroutine parameters



It can be used by user to store data for later use (store by PUSH, retrieve by POP).

R2: Status Register (SR)

The Status Register (SR/R2) stores the status bits and control bits.

Status Flags: Indicate some condition produced by an instruction execution.The system flags are changed automatically by the CPU depending on

the result of an operation.

C : Carry Flag : It is set to 1 , if a carry is generated in an Addition (or) borrow in Subtraction.

Z : Zero Flag : It is set to 1, if the result of an operation is ZERO.A common application of Zero flag is to check whether two values are

equal or not

N : Negative Flag : It is made equal to the MSB of the result. It is used with signed numbers only. N=1 for negative results and N =0 for positive results.

V: Signed overflow flag :It is set to 1, when the result of a signed operation has overflowed, even though a carry may not be generated. For ex., the sum of 0x75 + 0x67 = 0xDC. There is no problem if the variables are unsigned. But, if they are signed, the overflow flag will be set.

Enable Interrupts : Setting the general interrupt enable (GIE) bit enables maskable interrupts.

Clearing the bit disables all maskable interrupts. There are also nonmaskable interrupts, which cannot be disabled with GIE.

Control of Low-Power Modes :

The CPUOFF, OSCOFF, SCG0, and SCG1 bits control the mode of operation of the MSP430MCU.All systems are fully operational when all bits are clear. Setting combinations of these bits puts the device into one of its low-power modes.

SCG1 (System clock generator 1) : When set, turns off the SMCLK.

SCG0 (System clock generator 0) : When set, turns off the DCO dc generator,



if DCO-CLK is not used for MCLK or SMCLK.

OSCOFF (Oscillator OFF ) : When set, turns off the LF XT1 crystal oscillator, if LFXT1-CLK is not used for MCLK or SMCLK.

CPUOFF : When set, turns off the CPU.

R2/R3: Constant Generator Registers (CG1/CG2)

Depending of the source-register addressing modes (As) value, six commonly used constants can be generated without a code word or code memory access to retrieve them.

This is a very powerful feature, which allows the implementation of emulated instructions, for example, instead of implementing a core instruction for an increment, the constant generator is used.

The registers R2 and R3 can be used to generate six different constants commonly used in programming, without the need to add an extra 16-bit word of code to the instruction.

The constants below are chosen based on the bit (As) of the instruction that selects the addressing mode.

Register

Addressing mode

Constant

R2 10 +4R2 11 +8R3 00 0R3 01 +1R3 10 +2R3 11 -1

(FFFF)

The constant generator advantages are:• No special instructions required• No additional code word for the six constants• No code memory access required to retrieve the constant

The assembler uses the constant generator automatically if one of the 6- constants is used as an immediate source operand. Registers R2 and R3, used in the constant mode, cannot be addressed explicitly; they act as source-only registers.

Constant Generator - Expanded Instruction Set

The RISC instruction set of the MSP430 has only 27 instructions. However, the constant generator allows the MSP430 assembler to support 24 additional, emulated instructions. For example, the single-operand instruction

clr.w dst is replaced by : mov.w R3,dst



where the #0 is replaced by the assembler, and R3 is used with As = 00

inc.w dst is replaced by : add.w 0(R3), dst

R4 - R15: General–Purpose Registers :These general-purpose registers are used to store data values, address pointers, or index values and can be accessed with byte or word instructions.

11. ADDRESSING MODES :

The method of specifying data to be operated by an instruction is called as addressing mode. The different ways that a processor can access the data are referred to as addressing mode.

For MSP430, Seven addressing modes for the source operand and four addressing modes for the destination operand can address the complete address space with no exceptions.

S.No.

Addressing Mode

Syntax Description As /

Ad

1 Register mode Rn Register contents are operand 00 / 0

2 Indexed mode X(Rn) (Rn + X) points to the operand.

01 / 13 Symbolic mode

/ PC relative LABLE(PC + X) points to the operand. X = Offset address = Address of LABLE - PCIndexed mode X(PC) is used

4 Absolute mode &ADDRThe word following the instruction contains the absolute address. Indexed mode X(SR) is used, where X= ADDR, SR =0.

5 Indirect register mode @Rn Rn is used as a pointer to the operand. 10 / --

6 Indirect autoincrement @Rn+

Rn is used as a pointer to the operand. Rn is incremented afterwards by 1 for .B instructions and by 2 for .W instructions.

11 / --

7 Immediate mode #N The word following the instruction

contains the immediate constant N.

1. Register mode :

In this addressing mode, the data is available in any one of the registers in the CPU.

This is available for both source and destination



Ex: mov.w R5, R6 ; copies word from R5 to R6

2. Indexed mode :

In this addressing mode, the address of data is the sum of constant base address and the contents of a CPU register.

This mode is available for both source and destination

Ex: mov.b 3(R5), R6 ; load byte from address (3+R5) into R6If R5 = 0004 then, the content of memory address 0007 is

moved to R6

3. Symbolic mode / PC Relative :

In this addressing mode, PC is used as the base address. So the address of data is the sum of PC and relative offset address of data.

The assembler calculates the relative offset address of the data

Ex: mov.w LABLE, R6 ; load word LABLE into R6

The assembler replaces the above instruction by the indexed form

mov.w X(PC), R6 ; load word LABLE into R6

where X = relative offset = LABLE – PC

4. Absolute mode :

In this addressing mode, the absolute address of the data is available in the instruction.

This is already the complete address required, so that it should be added to a register that contains ZERO. Hence, in indexed addressing, the Status Register is used as constant generator (CG1) and it contains 0 when it is used as the base for indexed addressing.

Absolute addressing is shown by the prefix “ & ”

Ex: mov.b &P1IN, R6 ; load byte from port address P1IN into R6

The assembler replaces the above instruction by the indexed form

mov.b P1IN(SR), R6 ; load byte from port address P1IN into R6

The above instruction moves the content of source address to the register R6

5. Indirect Register mode :

In this addressing mode, the address of the data is available in the register.



Indirect register addressing is shown by the symbol @ in front of a register such as @R5. In other words, R5 is used as a pointer.

This mode is available for only source operand.

Ex: mov.w @R5, R6 ; load word from address (R5) into R6

If R5 = 0004 then, the content of memory address 0004 is moved to R6

6. Indirect Auto-increment Register mode :

In this addressing mode, the address of the data is available in the register.

This addressing mode is shown by the symbol @ in front of a register with + sign after it such as @R5+ . In other words, R5 is used as a pointer and it is automatically incremented by 1 for BYTE operation and 2 by WORD operation.


Ex: mov.w @R5+, R6 ; load word from address (R5) into R6 and increment R5 by 2

If R5 = 0004 then, the content of memory address 0004 is moved to R6 and

the pointer R5 is incremented by 2.

7. Immediate mode :

In this addressing mode, the data is available immediately after the instruction.

The PC is automatically incremented after the instruction is fetched and therefore points to the following word. Hence it is a special case of Indirect auto-increment register addressing mode.


Ex: mov.b #45, R6 ; move the immediate constant into R6.

mov.b @PC+, R6 ;



12. INSTRUCTION FORMATS OF MSP430 :

An instruction is a command given to the processor/controller to perform a given task on specified data. Each instruction has 2- parts:

(a) The task to be performed – called as Operation code (Opcode)(b) The data to be operated on – called as Operand.

Instruction OPCODE OPERAND

There are three core-instruction formats:(i) Dual-operand(ii) Single-operand(iii) Jump

The source and destination of an instruction are defined by the following fields:src : The source operand defined by As and S-reg



dst : The destination operand defined by Ad and D-regAs : Addressing bits responsible for the addressing mode used for the

source (src)Ad : Addressing mode used for the destination (dst)S-reg : The working register used for the source (src)D-reg : The working register used for the destination (dst)B/W : Byte or word operation:

0: word operation 1: byte operation

All single-operand and dual-operand instructions can be byte or word instructions by using .B or .W extensions. Byte instructions are used to access byte data (or) byte peripherals. Word instructions are used to access word data (or) word peripherals. If no extension is used, the instruction is a word instruction.

INSTRUCTION TIMINGS:

The number of CPU clock cycles required for an instruction depends on the instruction format and the addressing modes used - not the instruction itself.

The number of clock cycles refers to the MCLK. The number of MCLK cycles required for most instructions is limited by access to

memory.



The general principle for Format-I instructions (Two operands) is as follows :

(i) It takes one cycle to fetch the instruction word itself. This is all if both source and destination are in CPU registers.

Ex: mov.w R5, R6

(ii) One more cycle is needed to fetch the source if it is given indirectly as @Rn or @Rn+, in which case the address is already in the CPU. This includes immediate data.

Ex: mov.w @R5, R6

(iii) Alternatively, two more cycles are needed if one of the indexed modes is used. The first is to fetch the base address, which is added to the value in a CPU register to get the address of the source. A second cycle is necessary to fetch the operand itself. This includes absolute and symbolic modes.

Ex: mov.w 25(R5), R6

(iv) Two more cycle are needed to fetch the destination in the same way, if it is indexed.

Ex: mov.w @R5, 25(R6)

(v) A final cycle is needed to write the destination back to memory if required; no allowance is needed for a register in the CPU.

13. INSTRUCTION SET OF MSP430



The complete MSP430 instruction set consists of 27 core instructions & 24 emulated instructions.

The core instructions are instructions that have unique op-codes decoded by the CPU.

The emulated instructions are instructions that make code easier to write and read, but do not have op-codes themselves; instead they are replaced automatically by the assembler with an equivalent core instruction.

For the emulated instructions, the operand is always a destination.

(i) Movement Instructions (Data Transfer)(ii) Arithmetic and Logic Instructions(iii) Shift and Rotate Instructions(iv) Control Transfer instructions (Branch/Subroutine/Interrupt)

(i) Movement Instructions

Instruction Operation Example

1 mov.w src, dst

Copies data from source to destinationdst src

mov.w R5, R6R6 R5

2 push.w src

Push data onto stack ( first the SP is decremented by 2 and the source content is stored at stacktop)

@ --SP = src

push.w R5 SP SP-2@ SP R5

3 pop.w dst

Pop data from stack ( first the content of stacktop is moved to destination and SP is incremented by 2)

dst = @SP + +

push.w R6R6 @ SPSP SP+2

(ii) Arithmetic and Logic Instructions

(a) Binary Arithmetic Instructions with Two operandsInstruction Operation Example

1 add.w src, dst

Add the content of source to destinationdst dst + src

add.w R5, R6

2 addc.w src, dst

Add with carrydst dst + (src + C)

addc.w R5, R6

3 adc.w dst Add carry bit to the destination

dst dst + Cadc.w R6



4 sub.w src, dst Subtract the content of source from destination

dst dst - srcsub.w R5, R6

5 subc.w src, dst

Subtract with borrowdst dst –( src + C)

subc.w R5, R6

6 sbc.w dst Subtract borrow bit from the destination

dst dst – Csbc.w R6

7 cmp.w src,dst

Compares source and destination.Performs ( dst – src), but Only flags are changedIf dst > src : C=0, Z=0If dst < src : C=1, Z=0If dst = src : C=0, Z=1

cmp.w R5,R6

(b) Arithmetic Instructions with One operand :

All these instructions are emulated, which means that the operand is always a destination


1 clr.w dst Clear destination

dst 0clr.w R6R6 0

2 dec.w dst The content of destination is decremented by 1

dst dst – 1

dec.w R6R6 R6 - 1

3 decd.w dst

Double decrementThe content of destination is decremented by 2

dst dst – 2

decd.w R6R6 R6 – 2

4 inc.w dst The content of destination is inccremented by 1

dst dst + 1

inc.w R6R6 R6 + 1

5 incd.w dst

Double incrementThe content of destination is inccremented by 2

dst dst + 2

incd.w R6R6 R6 + 2

6 tst.w dst Test ( compare with zero)Performs ( dst – 0), but Only flags are changedIf dst > 0 : C=0, Z=0

tsd.w R6



If dst < 0 : C=1, Z=0If dst = 0 : C=0, Z=1

(c) Decimal Arithmetic Instructions :

These instructions are used to perform BCD addition


1 dadd.w src, dst

Perfroms the decimal addtion of destination and source with carry

dst dst + src + C

dadd.w R5, R6R6 R6 +

R5+C

2 dadc.w dst Performs the decimal addition of destination and carry.

dst dst + C

dadc.w R6R6 R6 + C

(d) Logic Instructions with Two operands


1 and.w src, dst

Performs bit-wise logic AND operationdst dst AND src

and.w R5, R6

2 xor.w src, dst Performs bit-wise logic Ex-OR operation

dst dst XOR srcxor.w R5, R6

3 bit.w src, dst Performs bit-wise Test operationIt performs Logic AND operation, But Only flags are affected

bit.w R5, R6

4 bis.w src, dst

Set bits in destinationThe source operand and the destination operand are logically ORed. The result is placed into the destination. The source operand is not affected.

dst dst OR src

bis.w R5, R6

5 bic.w src, dst

Clear bits in destinationThe inverted source operand and the destination operand are logically ANDed. The result is placed into the destination. The source operand is not affected

dst dst AND ~src

bic.w R5, R6

(e) Logic Instructions with ONE operand




1 inv.w dst

Invert destination Performs bit-wise NOT operation (1’s complement)

dst ~dst

inv.w R6

(f) Byte manipulationInstruction Operation Example

1 swpb dst Swap upper and lower bytesThe high and the low byte of the operand are exchanged

dst.15:8 ↔ dst.7:0swpb R6

2 sxt dst

Extend sign of lower byte The sign of the low byte of the operand is extended into the high byte

dst. 15:8 dst.7If dst.7 = 0: high byte = 00 H afterwardsIf dst.7 = 1: high byte = FF H afterwards

sxt R6

(g) Operations on Bits in Status Register

These instructions are used to set orclear the falgs in Status Register. All these instructions are emulated instructions.

Instruction Operation Flag affected

1 clrc Clear Carry bit C = 0

2 clrn Clear Negative bit N = 0

3 clrz Clear Zero bit Z = 0

4 setc Set Carry bit C = 1

5 setn Set Negative bit N = 1

6 setz Set Zero bit Z = 1

7 dint Disable General Interrupts GIE = 0

8 eint Enable General Interrupts GIE = 1

(iii) Shift and Rotate Instructions

Instruction Description Operation



rla dst Arithmetic shift Left

rra dst Arithmetic shift Right

rlc dst Rotate Left through Carry

rrc dst Rotate Right through Carry

(iii) Control Trasnfer Instructions

Instruction Description Operation

1 br src Branch ( go to) PC src

2 call src Call SubroutineSP SP-2

@ SP PCPC src

3 ret Return from Subroutine PC @ SPSP SP+2

4 reti Return from InterruptSR @ SPSP SP+2

PC @ SPSP SP+2

5 nop No operation ( consumes single cycle )

JUMP Instructions Condition1

jmp labelUnconditional Jump



2 jc / jlo label Jump if carry / Jump if lower Jump if C =1

3 jnc / jhs label Jump if not carry / Jump higher or same Jump if C =0

4 Jz / jeq label Jump if zero / Jump if equal Jump if Z =1

5 Jnz / jne label Jump if not zero / Jump if not equal Jump if Z =0

6 jn label Jumpif negative Jump if N =1

7 jge label Jump if greater or equal (signed values)

Jump if (N xor V) =0

8 jl label Jump if less than (signed values) Jump if (N xor V) =1

14. SAMPLE EMBEDDED SYSTEM ON MSP 430 :

Note : Write about the introduction to MSP430

The letters MSP stand for mixed signal processor, which is a reminder that many practical applications require analog inputs. There is a selection of analog-to-digital converters with a resolution of up to 16 bits. An example of a system where this choice is important is the weighing machine shown in above Figure. It includes the following functional blocks:

The sensor has four resistive elements arranged as a Wheatstone bridge. Ideally, this is balanced when there is no load, giving V+ = V− . Two of the



resistances increase and two decrease when a weight is placed on the scale pan, driving the bridge out of balance.A differential amplifier magnifies the difference in voltage between its input terminals, giving Vout = A(V+ −V−), where A is the gain.The analog output of the amplifier is converted to a binary value by A/D converter.The microcontroller multiplies the input by an appropriate factor so that the display gives the weight in grams or ounces and subtracts an offset so that the display reads zero when no weight is present. It also reads the buttons and supervises the complete system.There is a serial interface between the microcontroller and the liquid crystal display, which has a built-in controller.

This system clearly needs a lot of components, including several integrated circuits. In contrast, the whole system can be constructed from a sensor, an MSP430F42x, a simple LCD without a controller, and a couple of decoupling capacitors. The MSP430x4xx family drives segmented LCDs directly, which eliminates the need for a controller. Several devices contain ADCs with high-resolution, differential inputs, which would work directly from the sensor without the need for an amplifier. The microcontroller can also manage the power drawn by the circuit so that the processor would be switched off when it was not needed and the whole system shut down after a period of inactivity.


Documents

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