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 Post subject: data too much for eeprom
PostPosted: Wed Sep 27, 2006 8:05 pm 
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Joined: Fri Jul 28, 2006 12:12 am
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If I have a 12KB application that I want to burn to eeprom, can I burn in to two 8KB ROMs. What I mean is can I span it over two 8KB ROM's or do I need to buy one 16KB EEPROM?

My logic tells me I should be ablel to span it, but then, who am I.


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PostPosted: Wed Sep 27, 2006 8:15 pm 
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Joined: Fri Aug 30, 2002 9:02 pm
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Location: Sacramento, CA
Yes, you can span multiple EEPROMs. You just need to be sure each EEPROM's address space is properly decoded in your hardware.

Daryl


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PostPosted: Wed Sep 27, 2006 11:03 pm 
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which may mean more parts in your glue logic and more logic delays, reducing your maximum speed. Do you have a really old programmer that does not handle 16Kx8 EPROMs gracefully?


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PostPosted: Sat Sep 30, 2006 5:10 pm 
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GARTHWILSON wrote:
which may mean more parts in your glue logic and more logic delays, reducing your maximum speed. Do you have a really old programmer that does not handle 16Kx8 EPROMs gracefully?


Not the way I see it. If he's using a 74LS138 to 'divide' the memory map into chunks of 8K then it's just a matter of attaching the two EEPROM's sequentially (say on outputs 6 and 7).

If you can find yourself a Linux/BSD/UNIX system, kernal34, you can use these commands to split the eeprom image into two seperate files:

dd bs=8192 count=1 if=original.bin of=lower.bin
dd bs=8192 count=1 skip=1 if=original.bin of=upper.bin

which should give you two files, lower.bin and upper.bin, created from original.bin.

bs is block size (8K in this case), count is the number of blocks to copy, skip is the number of blocks to skip before reading, if is the input file, of is the output file.

Good luck.

_________________
Check out my 8080 project: http://kaput.homeunix.org


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PostPosted: Sat Sep 30, 2006 7:01 pm 
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Quote:
If he's using a 74LS138 to 'divide' the memory map into chunks of 8K then it's just a matter of attaching the two EEPROM's sequentially (say on outputs 6 and 7).
True, and that's the way I did it with my first home-made computer; but you'll get more logic delays that way. You'll have less wire-up work and a smaller board too if you can put it all in one ROM socket and just use a 16Kx8 or 32Kx8 ROM.


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PostPosted: Wed Oct 11, 2006 4:41 pm 
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Thanks guys...


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