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EEPROM size auto-detect

 
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Richard Slater



Joined: 08 Sep 2003
Posts: 12
Location: Cambridge, UK

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EEPROM size auto-detect
PostPosted: Wed Jan 29, 2003 10:04 am     Reply with quote

Hello good people!

Is it possible to auto-detect the size of an EEPROM, such as the 24LCxx range, so I can change (or remove altogether) the type of EEPROM from one PCB to the next, without changing the code?

If it is, a few hints would be appreciated!

Thanks

Richard
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Original Post ID: 11096
kolio
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Re: EEPROM size auto-detect
PostPosted: Thu Jan 30, 2003 3:52 am     Reply with quote

:=Hello good people!
:=
:=Is it possible to auto-detect the size of an EEPROM, such as the 24LCxx range, so I can change (or remove altogether) the type of EEPROM from one PCB to the next, without changing the code?
:=
:=If it is, a few hints would be appreciated!
:=
:=Thanks
:=
:=Richard

Hi,
EE size auto-detect is possible, but will cost some program memory. 24xx family members have different architectures. There are several 24xx.C files in CCS include subfolder. The main differencies are in the comm protocol. 2401-2416 have 1-byte address, while 2432 and above have 2-byte address. You need to make your own read/write routines, where ACK return from i2c_write should be checked. It's good to have control on 24xx WP pin to prevent undesired write operation.
First, read random with 1-byte address protocol. If all the ACKs are issued by 24xx this means you're in the right group. Otherwise, check with 2-byte address.
Second, random write 0xAA and 0x55 to the last assumed address and then verify the value. If the result is negative, ADDR>>1 and try again.
Write test may damage any previously stored info in 24xx, so before write, you can read and store the value and restore it later.
Wish you luck,
Kolio
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Original Post ID: 11133
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