Using Virtual EEPROM and Flash API for Renesas MCUs (1)

Class ID:
Renesas Electronics America Inc.
© 2012 Renesas Electronics America Inc. All rights reserved.
Using Virtual EEPROM and Flash API for
Renesas MCUs
© 2012 Renesas Electronics America Inc. All rights reserved.2
Renesas Technology & Solution Portfolio
© 2012 Renesas Electronics America Inc. All rights reserved.3
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, Performance
1200 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-bit8/16-bit
32-Bit High Performance
DSP, FPU with High Integration
© 2012 Renesas Electronics America Inc. All rights reserved.4
 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’
© 2012 Renesas Electronics America Inc. All rights reserved.5
Agenda
 Introduction to Virtual EEPROM
 Features
 How does it work?
 Configuration
 API

Lab
© 2012 Renesas Electronics America Inc. All rights reserved.6
Terminology
 Non-volatile Data
 Record
 EEPROM

 Erase and write sizes (or granularity)
© 2012 Renesas Electronics America Inc. All rights reserved.7
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
© 2012 Renesas Electronics America Inc. All rights reserved.8
The Problem – Storing Non-Volatile Data
 Store in external EEPROM
 Advantages:
 Self-contained
 Easy to use
 Usually 1 byte writable
 Disadvantages:
 $$$
 Uses HW
 No record management
© 2012 Renesas Electronics America Inc. All rights reserved.9
The Problem – Storing Non-Volatile Data
 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
© 2012 Renesas Electronics America Inc. All rights reserved.10
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
© 2012 Renesas Electronics America Inc. All rights reserved.11
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
© 2012 Renesas Electronics America Inc. All rights reserved.12
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
I2C
© 2012 Renesas Electronics America Inc. All rights reserved.13
Simple API
User Application
R_VEE_Write(my_record)


R_VEE_Read(my_record)

MCU
ROM
Data Flash
© 2012 Renesas Electronics America Inc. All rights reserved.14
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
© 2012 Renesas Electronics America Inc. All rights reserved.15
Virtual EEPROM Features
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Background Operations (BGO)
 With BGO, MCU can continue during DF erase or write
 Memory area being worked on cannot be accessed
Access Violation!
© 2012 Renesas Electronics America Inc. All rights reserved.17
Wear Leveling
 Increases longevity of the Data Flash
 Records do not overwrite
 Old records are ignored
VEE Memory Area
Address
0x100000
Address
0x1007FF
VEE
Record
1
VEE
Record
1
VEE
Record
2
VEE
Record
1

VEE
Record
2
© 2012 Renesas Electronics America Inc. All rights reserved.18
Ignore Duplicate Writes
 Increases longevity of the Data Flash
 Identical writes are ignored
 Time trade-off
VEE Memory Area
Address
0x100000
Address
0x1007FF
VEE
Record
1
VEE
Record
1
VEE
Record
2
VEE
Record
1
CHECKING…
VEE
Record
2
© 2012 Renesas Electronics America Inc. All rights reserved.19

Record Caching
 No seeking for records
 1 cache entry per available record number
VEE Memory Area
Address
0x100000
Address
0x1007FF
VEE Record Cache
Record 1
Address
Record 2
Address
VEE
Record
1
VEE
Record
1
VEE
Record
2
VEE
Record
1
VEE
Record
2
Many More
Records

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VEE Memory Area
VEE
Record
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
© 2012 Renesas Electronics America Inc. All rights reserved.21
Overhead
 4 extra structure members per record

Overhead depends on write granularity
 RX62N = 32 bytes per record
 RX63N = 8 bytes per record
© 2012 Renesas Electronics America Inc. All rights reserved.22
How does it work?
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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
© 2012 Renesas Electronics America Inc. All rights reserved.24
Virtual EEPROM Operational Overview
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
© 2012 Renesas Electronics America Inc. All rights reserved.25
Virtual EEPROM Operational Overview
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
VEE Record 1
NOT ENOUGH
ROOM