attiny167-esxz ATMEL Corporation, attiny167-esxz Datasheet - Page 208

• Manufacturer Part Number: attiny167-esxz
• Description: 8-bit Avr 8-bit Microcontroller Microcontroller With 16k Bytes In-system Programmable Flash And Lin Controller
• Manufacturer: ATMEL Corporation

20. Flash Programming
20.1
20.1.1
20.1.2
208
Self-Programming the Flash
ATtiny167
Performing Page Erase by SPM
Filling the Temporary Buffer (Page Loading)
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
Program 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:
•
•
If only a part of the page needs to be changed, the rest of the page must be stored (for example
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 alter-
native 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.
To execute Page Erase, set up the address in the Z-pointer, write “00000011
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.
•
To write an instruction word, set up the address in the Z-pointer and data in R1:R0, write
“00000001
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.
Alternative 1, fill the buffer before a Page Erase
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Alternative 2, fill the buffer after Page Erase
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–
–
The CPU is halted during the Page Erase operation.
Fill temporary page buffer
Perform a Page Erase
Perform a Page Write
Perform a Page Erase
Fill temporary page buffer
Perform a Page Write
b
” to SPMCSR and execute SPM within four clock cycles after writing SPMCSR. The
b
” to SPMCSR and
7728A–AUTO–07/08