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[SOLVED] problem in writing FLASH memory of AVR via ISP

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vinodstanur

vinodstanur

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I am trying to read and write FLASH and EEPROM of an AVR (atmega8) via ISP.
I had programmed a PIC16F877A which accepts 8 bit data from UART (hyperterminal) and send it to AVR via SPI at reset zero...

I have successfully enabled the ISP mode by sending
cmd(0xac, 0x53, 0, 0); also verified the return byte.

Now I can write and read back the EEPROM without any problem..
for example,
cmd(c0,00,11,AB) writes AB at 11 of eeprom
Now I could read it by
cmd(a0,00,11,xx)
NO PROBLEM UPTO THIS...

Now,
when I am tying to write and read the FLASH, I am always gettign 0xff while reading,,,

I used command 60,68 to write and 20,28 to read (lower byte and higher byte respectively)

But ALWAYS READING 0XFF even if I modify it...
what may be the problem ?
 

vinodstanur said:
when I am tying to write and read the FLASH, I am always gettign 0xff while reading,,,

I used command 60,68 to write and 20,28 to read (lower byte and higher byte respectively)
Click to expand...
I haven't faced the ISP challenge yet, but I found this reference from ATMEL:
http://www.atmel.com/dyn/resources/prod_documents/doc0943.pdf

page 7:
In some devices, there is no method to detect when the Flash write cycle has ended. For this
reason, the programmer presented in this application note waits N ms before attempting to send
another command to the interface (the delay N will depend on target device, and can be found in
the programming section of the datasheet). For some devices it is possible to use polling. When
a byte is being programmed into the Flash or EEPROM, reading the addressed location being
programmed will give a value M (often $FF). At the time the device is ready for a new byte, the
programmed value will read correctly. This can be used to determine when the next byte can be
written. When programming the value M polling will not work, and a delay N should be used
before writing the next value. Polled mode will decrease the time required to program a device
Click to expand...
 

The Flash is programmed one page at a time.
Click to expand...

I conudn't understand how we write flash by one page at a time..
More over, I think it is not explained in data sheet and the ISP application note..
 

vinodstanur said:
I conudn't understand how we write flash by one page at a time..
More over, I think it is not explained in data sheet and the ISP application note..
Click to expand...

Yes you are right in this reference it is not explained. There is a possibility that the page write proccess is MCU dependent. Maybe you could take a look at some AVR datasheets and find that out.
Just an assumption... :smile:
 
Last edited:

I just looked into the USBASP source code (isp.c) but still I couldn't makeout....:(

I can write and read EEPROM but not FLASH...
 

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