System on a Chip (SoC)

Lin ZhongELEC424, Fall 2010

Photolithography

1969

Ivan Sutherland won Turing Award in 1988 for his Ph.D. work in 1963

http://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-574.pdf

“System on board”

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“System on board” (Contd.)

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Multiple Chip Modules (MCM)

• Intel Pentium D, Core 2 Quad

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IBM POWER5 (2004) MCM, used in IBM system p servers, four dual core processors + four L3 cachesWikipedia.org

System in Package (SiP)

Siemens SX66 PDA PhoneAudiovox PPC6601KIT

32MB

400MHz

Source: Intel.com

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System-on-a-chip (SoC): TI OMAP

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System-on-a-chip (SoC): TI MSP430

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Functional block diagram

Inside a CPU (Micro-architecture)IBM POWER5 die photo (2004)

• FXU: fixed-point execution unit• ISU: instruction sequencing unit• IDU: instruction decode unit• LSU: load/store unit• IFU: instruction fetch unit• FPU: floating-point unit• MC: memory controller

12Sinharoy et al 2005

Components of SoC

• Processors• Clock generator• Flash memory & controller• DMA & controller• Digital I/O modules• Programming interface• Interconnection

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Embedded processors

• Microprocessor (32bit beyond)– ARM, MIPS, PowerPC, SuperH– Usually very modern architectures– ARM: Most popular 32bit embedded processor (75%)

• Assignment: read “ARM architecture” from Wikipedia

• Microcontroller (4-16bit)– Harvard architecture– 8051 (8bit), PIC (8bit), AVR from Atmel (8bit)– MSP430: 16-bit RISC, von Neumann architecture

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Clock generator

• Resonant circuit + amplifier

• Resonant circuit (Oscillator)– Crystal oscillator (>2x109/yr)

• ~10KHz to ~10MHz• Quartz, ceramics (low cost, low accuracy), surface acoustic

wave (SAW) quartz crystal (expensive, accurate)• Real-time clocks

– 32.768KHz (215), 4.194304MHz (222)

• Application-specific– 4.9152MHz (4 x 1.2288MHz, CDMA baseband frequency)……

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ResA

• LC/RLC circuit• Ring oscillator

– Application other than oscillator?• Voltage-controlled oscillator (VCO)

– Varicap: variable capacitance diode (tuning diode)– Phase-locked loop for high-speed clock (next slide)– Frequency scaling of IC for energy saving

Oscillator (Contd.)

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• High-speed clock from a master oscillator• Digital PLL

• Clock generation, recovery, synchronization– Digital computing, RF communication

Phase-locked loop (PLL)

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Phase-frequency detector

Master oscillator

VCO

Frequency divider (N)

voltage

MSP430 clock modules

• Clock sources– External oscillators

• Low- oscillator (LFXT1CLK): usually 3.2768KHz (RTC)• Optional high-frequency oscillator (XT2CLK)

– Internal digitally controlled oscillator (DCO) (DCOCLK) (power hungry)

• Clock signals– Auxiliary clock: divided LFXT1CLK (1, 2, 4, 8)

• For low-power standby

– Master clock: any source, divided by 1, 2, 4, or 8– Sub-system clock: XT2CLK or DCOCLCK, divided by 1, 2, 4, or 8

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DCO (Contd.)

• Ring oscillator with RC-type characteristics• Software controllable

– On/Off– Frequency

– External resistor allows low temperature impact, higher frequency

• Impacted by temperature , supply voltage, and process variations (inter-chip variations)

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8 internal and 1 external resistors

Flash Memory and Controller

• Non-volatile, semiconductor memory– Limited # of erase cycles wear leveling

• NOR Flash: slow write/erase, random access– ROM replacement

• NAND Flash: faster write/erase, block access, denser, more enduring– Harddisk replacement

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MSP430 Flash memory controller

• NOR flash (for program)– No need for wear leveling (100K to 1M erase cycles)

• In-system programmable (ISP)– Self programming, program via wireless

• Programming through JTAG, UART (Bootstrap loader, BSL)

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Digital I/O Modules

• USART – Universal synchronous/asynchronous

receiver/transmitter– Asynchronous: UART– Synchronous: SPI, I2C

• UART (2-4 wires)– Easily work with RS-232 (serial port), modem,

Bluetooth (Serial Port Profile)– Baud rate, # of data bits, optional parity bit, flow

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MSP430 UART

• Two UART ports, each two pins• Support interrupt• No hardware flow control• <200Kbps

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Serial interfaces

• Inter-Integrated Circuit (I2C)– Two wires– Standard mode: 100Kbps– Fast mode: 400Kbps– System management bus (SMBus): 100Kbps

• Serial Peripheral Interface (SPI)– 4 wires: Clock, Chip Select, In and Out– Low-megahertz data rate

wikipedia.org

Universal Serial Bus (USB)

• Replacing all serial/parallel ports– All phones in China use USB for power

• Host vs. device• USB 1.0: low-speed, 1.5Mbps

– Human interface devices– 1.5A power supply– USB 1.1: full-speed, 12bBps

• USB 2.0: high-speed, 480Mbps– Storage devices, Wi-Fi cards etc.– 900mA power supply

• USB 3.0: super-speed, 4.8Gbps

Analog I/O

• Analog-digital conversion (ADC)– Voltage measurement– Sensing the world through voltage

• XXX voltage

• Digital-analog conversion (DAC)– Actuator

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ADC

• Resolution: how many bits for “D”?– 24bits max– MSP4301611: 12 bits

• Sampling rate: how fast?– MSP430: up to 200Ksps

• Accuracy– Quantization error etc.

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Interrupt

• Polling vs. interrupt

• Non-maskable vs. maskable

• Nested interrupt

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Interrupt handler

Save context

Retrieve context

Interrupt

• Programmable interrupt controller (PIC)– Prioritizing multiple sources– Offloading the CPU

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PIC CPU

Interrupt

Interrupt vector

Interrupt sources (external devices)

Exceptions, signals, & interrupts

• Exceptions– Any disruption of normal execution to execute

special instructions• Signals

– Inter-process communication• Interrupt

– Asynchronous exception introduced by external hardware

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Timer

• Count time– Keep time

• How many cycles have elapsed

– Measure time• Whether a given period of time elapsed

• Generate interrupt

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Capture registerClock

Compare registerComparator

Interrupt

Direct memory access (DMA)

• Free CPU from data transfer• Multiple channels, master bus, interrupt CP when done

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DMA (Contd.)

• Character mode• Block mode

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Power-saving mechanisms

• Frequency scaling (slow down)– DCO

• Power saving modes

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Miscellaneous

• Pulse-width modulation (PWM)

– Applications: power delivery (charging, light, motor), sound synthesis• Watchdog timer

– Reset system under fault• Brownout reset

– Reset system when supply voltage low

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