Class ID: Renesas Electronics America Inc. © 2012 Renesas Electronics America Inc. All rights reserved. Class ID: Using Virtual EEPROM and Flash API for

Class ID:

Renesas Electronics America Inc.© 2012 Renesas Electronics America Inc. All rights reserved.

Class ID:

Using Virtual EEPROM and Flash API for Renesas MCUs

CL08I

Brandon Hussey, Applications Engineer

© 2012 Renesas Electronics America Inc. All rights reserved.2

Brandon Hussey

Applications Engineer RX support

– Flash API – Virtual EEPROM– Flash Loader

Firmware Integration Technology (FIT)

PREVIOUS EXPERIENCE: Interned at Renesas for 3 years Joined on full-time after graduation

I hold an MSCPE from North Carolina State University


Renesas Technology & Solution Portfolio


Microcontroller and Microprocessor Line-up

Wide Format LCDs Industrial & Automotive, 130nm 350µA/MHz, 1µA standby

44 DMIPS, True Low Power

Embedded Security, ASSP

165 DMIPS, FPU, DSC

1200 DMIPS, Performance1200 DMIPS, Superscalar

500 DMIPS, Low Power

165 DMIPS, FPU, DSC

25 DMIPS, Low Power

10 DMIPS, Capacitive Touch

Industrial & Automotive, 150nm 190µA/MHz, 0.3µA standby

Industrial, 90nm 200µA/MHz, 1.6µA deep standby

Automotive & Industrial, 90nm 600µA/MHz, 1.5µA standby

Automotive & Industrial, 65nm 600µA/MHz, 1.5µA standby Automotive, 40nm

500µA/MHz, 35µA deep standby

Industrial, 40nm 200µA/MHz, 0.3µA deep standby

Industrial, 90nm 1mA/MHz, 100µA standby

Industrial & Automotive, 130nm 144µA/MHz, 0.2µA standby

2010 2012

32-b

it8/1

6-b

it

32-Bit High PerformanceDSP, FPU with High Integration


Devices in a smart society must efficiently use their available resources. Eliminating the need for external components when they can be incorporated inside the MCU is vital.

‘Enabling The Smart Society’


Agenda

Introduction to Virtual EEPROM

Features

How does it work?

Configuration

API

Lab


Terminology

Non-volatile Data

Record

EEPROM

Erase and write sizes (or granularity)


MCU

ROM

The Problem – Storing Non-Volatile Data

Store in internal ROM

Advantages:

Stored internally to MCU; no extra

cost

Disadvantages:

Must halt MCU or run from RAM

Possibility of corrupting application

Relatively large minimum write and

erase sizes

Complex to implement



Store in external EEPROM

Advantages:

Self-contained

Easy to use

Usually 1 byte writable

Disadvantages:

$$$

Uses HW

No record management

EEPROM



Store in internal data flash

Advantages:

Stored internally to MCU; no extra cost

Can continue to execute from ROM

Relatively small minimum write and erase sizes

No possibility of corrupting ROM

Disadvantages:

No record management

Write granularity might not be 1-byte

MCU

ROM

Data Flash

MCU


The Solution – Data Flash & Record Management

Use data flash and existing Flash API for low level

Add layer to handle record management

Flash API

???Virtual EEPROM


Data Flash Block #0

Data Flash Block #1

EMPTY

Why is Virtual EEPROM Needed?

Many data flashes do not have 1-byte writes

Maintaining multiple records

Statically allocating addresses can wear out DF faster

Using advanced features of MCU

Data #1 Data #2 EMPTY


MCU

ROM

Data Flash

What is the Virtual EEPROM Project?

The Virtual EEPROM Project allows you to use the Data Flash on your MCU as you would an EEPROM while adding other record management features

MCU

ROM

Data Flash/VEE

EEPROMI2C


Simple API

User Application

R_VEE_Write(my_record)......R_VEE_Read(my_record)...

MCU

ROM

Data Flash


Data Flash vs ROM

Typically Data Flash has:

Smaller write and erase sizes

Shorter write times

Larger number of rewrite/erase cycles

MCU – Memory Area

Write Size

Erase Size

Write Time

Erase Time

Erase/ Write Cycles

RX62N - DF 8B 2KB 0.4ms 70ms 30,000

RX62N - ROM 256B 4KB 2.0ms 25ms 1,000

RX63N – DF 2B 32B 0.25ms 2ms 100,000

RX63N – ROM 128B 4KB 1.0ms 25ms 1,000

MCU – Memory Area

Write Size

Erase Size

Write Time

Erase Time

Erase/ Write Cycles

RX62N - DF 8B 2KB 0.4ms 70ms 30,000

RX62N - ROM 256B 4KB 2.0ms 25ms 1,000


Virtual EEPROM Features


Background Operations (BGO)

With BGO, MCU can continue during DF erase or write

Memory area being worked on cannot be accessed

Access Violation!


Wear Leveling

Increases longevity of the Data Flash

Records do not overwrite

Old records are ignored

VEE Memory AreaAddress 0x100000

Address 0x1007FF

VEERecord

1

VEERecord

1

VEERecord

2

VEERecord

1

VEERecord

2


Ignore Duplicate Writes

Increases longevity of the Data Flash

Identical writes are ignored

Time trade-off


Address 0x1007FF

VEERecord

1

VEERecord

1

VEERecord

2

VEERecord

1CHECKING…

VEERecord

2


Record Caching

No seeking for records

1 cache entry per available record number


Address 0x1007FF

VEE Record Cache

Record 1 Address

Record 2 Address

VEERecord

1

VEERecord

1

VEERecord

2

VEERecord

1

VEERecord

2

Many More Records


VEE Memory Area

VEERecord

2

Error Detection

Each record has its own error detection field

Virtual EEPROM recovers automatically from errors

Recovery measures are only taken on writes

VEE Record 1

• ID • Size• Data• Check


Overhead

4 extra structure members per record

Overhead depends on write granularity

RX62N = 32 bytes per record

RX63N = 8 bytes per record


How does it work?


Virtual EEPROM Terminology

VEE Sector 0

VEE Block 0 VEE Block 1

VEE Record 0

VEE Record 1

VEE Record 1

VEE Record 0

VEE Record 2

VEE Record 2


Virtual EEPROM Operational Overview

VEE Sector 0


VEE Record 0

VEE Record 1

VEE Record 1

VEE Record 0

VEE Record 2

VEE Record 2



VEE Sector 0


VEE Record 0

VEE Record 1

VEE Record 1

VEE Record 0

VEE Record 2

VEE Record 2

VEE Record 1

NOT ENOUGH ROOM



VEE Sector 0


VEE Record 0

VEE Record 1

VEE Record 1

VEE Record 0

VEE Record 2

VEE Record 2

DEFRAG OCCURS

VEE Record 1

VEE Record 1



VEE Sector 0


VEE Record 0

VEE Record 1

VEE Record 1

VEE Record 0

VEE Record 2

VEE Record 2

VEE Record 1

VEE Record 0

VEE Record 2

DEFRAG CONTINUES



VEE Sector 0


VEE Record 0

VEE Record 1

VEE Record 1

VEE Record 0

VEE Record 2

VEE Record 2

VEE Record 1

VEE Record 0

VEE Record 2

DELETE OLD BLOCK



VEE Sector 0


VEE Record 1

VEE Record 0

VEE Record 2


Virtual EEPROM Configuration


Why would I need more than 1 VEE Sector?

Optimize (lower) the number of defrags

VEE Sector #0 – Block #0

VEERecord

1

VEERecord

2


VEERecord

2

VEERecord

2

VEERecord

2

VEERecord

1

VEERecord

2

VEERecord

2

VEERecord

2

VEERecord

2

Defrag Again!

1 Sector


Why would I need more than 1 VEE Sector?

Optimize (lower) the number of defrags


VEERecord

1


VEERecord

2

VEERecord

2

VEERecord

2

VEERecord

2

VEERecord

2

VEERecord

2

VEERecord

2

VEERecord

2

VEERecord

2

VEERecord

2

Defrag Finally!

2 Sectors


Virtual EEPROM API


API Functions

R_VEE_Read()

R_VEE_Write()

R_VEE_Defrag()

R_VEE_Erase()

R_VEE_GetState()

R_VEE_ReleaseState()


VEE Operation Completion

Can use polling or interrupt driven

Polling:

Use R_VEE_GetState()

Will return current state of VEE

Interrupt Driven:

User defined callback in r_vee_config.h

Warning: Callback is called from interrupt

#define VEE_CALLBACK_FUNCTION VEE_OperationDone_Callback


Data Flash User Application

Why do we need R_VEE_ReleaseState()?

Used to prevent data flash access violations

R_VEE_Read(ID=0) to read VEE Record 0

R_VEE_Write(ID=1) to write VEE Record 1

User reads data from pointer in step 1 while write is still on-going

Multiple reads are allowed

Pointer to Record 0VEE Record 0

VEE Record 1 VEE Record 1


Why not have R_FlashRead() instead?

User would call this function to read data

Advantages:

This would eliminate need for releasing state

Disadvantages:

RX can directly read data flash

Large overhead

Data would have to be copied every time

No way to prevent user from directly accessing


Virtual EEPROM for RL78


RL78 – EEPROM Emulation Library

Has similar features

Uses ‘pools’


RL78 – EEL Modes

Has 3 execution modes


Summary

Why do you need it?

Features

How it works

How to use it

Available on RX and RL78 MCUs


Questions?


Devices in a smart society must efficiently use their available resources. Eliminating the need for external components when they can be incorporated inside the MCU is vital.

‘Enabling The Smart Society’


Please utilize the ‘Guidebook’ application to leave feedback

or

Ask me for the paper feedback form for you to use…

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Renesas Electronics America Inc.© 2012 Renesas Electronics America Inc. All rights reserved.

Documents

Class ID: Renesas Electronics America Inc. © 2012 Renesas Electronics America Inc. All rights reserved. Class ID: Using Virtual EEPROM and Flash API for