PCIF0 datasheet(228/294 Pages) ATMEL

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228

9219A–RFID–01/11

Atmel ATA5505 [Preliminary]

21. Flash Programming

The device provides a Self-Programming mechanism for downloading and uploading program

code by the MCU itself. The Self-Programming can use any available data interface (i.e. LIN,

USART, ...) and associated protocol to read code and write (program) that code into the Pro-

gram memory.

The Program memory is updated in a page by page fashion. Before programming a page with

the data stored in the temporary page buffer, the page must be erased. The temporary page

buffer is filled one word at a time using SPM and the buffer can be filled either before the Page

Erase command or between a Page Erase and a Page Write operation:

• Alternative 1, fill the buffer before a Page Erase

– Fill temporary page buffer

– Perform a Page Erase

– Perform a Page Write

• Alternative 2, fill the buffer after Page Erase

– Perform a Page Erase

– Fill temporary page buffer

– Perform a Page Write

If only a part of the page needs to be changed, the rest of the page must be stored (for exam-

ple in the temporary page buffer) before the erase, and then be re-written. When using

alternative 1, the Boot Loader provides an effective Read-Modify-Write feature which allows

the user software to first read the page, do the necessary changes, and then write back the

modified data. If alternative 2 is used, it is not possible to read the old data while loading since

the page is already erased. The temporary page buffer can be accessed in a random

sequence. It is essential that the page address used in both the Page Erase and Page Write

operation is addressing the same page.

21.1

Self-Programming the Flash

21.1.1

Performing Page Erase by SPM

To execute Page Erase, set up the address in the Z-pointer, write “00000011

b” to SPMCSR

and execute SPM within four clock cycles after writing SPMCSR. The data in R1 and R0 is

ignored. The page address must be written to PCPAGE in the Z-register. Other bits in the

Z-pointer will be ignored during this operation.

• The CPU is halted during the Page Erase operation.

21.1.2

Filling the Temporary Buffer (Page Loading)

To write an instruction word, set up the address in the Z-pointer and data in R1:R0, write

“00000001

b” to SPMCSR and execute SPM within four clock cycles after writing SPMCSR.

The content of PCWORD in the Z-register is used to address the data in the temporary buffer.

The temporary buffer will auto-erase after a Page Write operation or by writing the CTPB bit in

SPMCSR. It is also erased after a system reset. Note that it is not possible to write more than

one time to each address without erasing the temporary buffer.

If the EEPROM is written in the middle of an SPM Page Load operation, all data loaded will be

lost.

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