Atmel ATEVK525 Betriebsanweisung PDF herunterladen (Seite 17)

Software Implementation

ATEVK525 Mass Storage Board for AVR 3-17

7740B–AVR–03/08

3.2 Performances

3.2.1 Benchmark

Table 3-1 . Memory speed benchmark (8MHz clocked microcontroller

(1)

)

Note: 1. The AVR micro controller cannot be clocked at 16MHz since this configuration

requires a 4.5V minimum power supply whereas NAND Flash or SD/MMC devices do

not withstand such a voltage level on I/Os. However, DataFlash are 5V-tolerant, and

speed measurements have been done independently of this evaluation board: for

45DB321, write speed is 40KB/sec and read speed is 300KB/sec. For 45DB642,

write speed is 80KB/sec and read speed is 300KB/sec.

2. In the K9K2G08UOM device, the COPYBACK instruction cannot be used in all the

memory plane, since it is efficient only between size-limited zones. This problem con-

cern several other memorie devices.

3.2.2 Direct limitations

 The limitations on reading operations are:

– Dataflash: SPI bus frequency, internal read access speed

– SD/MMC: SPI bus frequency, internal read access speed

– NAND Flash: USB maximum data rate

 The limitations on writing operations are:

– Dataflash: internal write access speed, page write duration & size, SPI bus

frequency

– SD/MMC: internal write access speed and duration, SPI bus frequency

– NAND Flash: memory internal writing structure (COPYBACK support or not,

page write and block erase duration, page size), USB maximum data rate

Memory

Speed (KBytes/sec)

Read Write

DataFlash AT45DB321 (page 512B) 200 35

AT45DB642 (page 1024B) 200 55

MMC/SD SD 1GB 80x 235 235

SD 256MB 215 155

MMC Plus 2GB Premium 235 170

MMC 32MB (old revision) 215 50

NAND Flash M29F2G008AAC (page 2KB, copyback) 1095 860

K9K2G08UOM (page 2KB, copyback disabled

(2)

) 1005 660

HYF31DS512805 (page 512B, no copyback) 1110 590

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Atmel ATEVK525 Betriebsanweisung Seite 17