How to set AVR to emulate EEPROM over SPI?
I would like to boot my TI's Piccolo from Atmel AVR AR32UV3A0512 via SPI port. Piccolo has a feature that allows it to boot through SPI connected EEPROM. TI documentation specifies that if the SPI is connecting to device other than EEPROM, the device should emulate EEPROM.
Does anyone know what is needed to do to make AR32UV3A0512 emulate EEPROM? Any hint or link towards proper documentation will be appreciated. I have not found any useful information in AVR documentation.
You need to program your Atmel AVR so that it transfers code to the Piccolo's internal memory using the appropriate data transfer flow. The data transfer flow depends on the chosen emulation boot mode. Keep in mind that you are not restricted to SPI emulation boot mode. You can use any of the following:
SPI
I2C
SCI
Parallel GPIO
SPI boot mode will not necessarily be the easiest one to implement. Anyways, the whole rigamarole comes down to two steps:
Step 1 (easy step): Choose an emulation boot mode, and configure the Piccolo accordingly, as described in the Bootloader Modes section of this doc: http://www.ti.com/lit/ug/sprugo0b/sprugo0b.pdf
Step 2 (hard step): Depending on the emulation boot mode you chose in step 1, you will need to program your Atmel AVR microcontroller to follow the respective data transfer flow. For example, if you chose SPI mode, then you must program your Atmel AVR to follow the transfer flow described in the SPI_Boot Function section of the above doc.