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V8MeatHead
Joined: 18 Jul 2005
Posts: 10
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 Posted: Thu Jan 25, 2007 2:48 am Post subject: What's Odd/Even arrangement with EPROMs what does it do? |
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| I'm familiar with eproms and electronics but what does the odd/even arrangement do to the bits on 2 eproms? What's an odd/even bit? Are even bits just the data at 'even' numbered addresses? What's the advantage to this and why do it? Thanks guys. Anything else you want to share please do. It's appreciated. |
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Oggie
Joined: 20 Mar 2005
Posts: 19
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| Posted: Thu Jan 25, 2007 10:38 am Post subject: |
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Odd and even arrangement is as you surmised - the odd numbered addresses go in one EPROM, then even numbered in the other. Typically this is used so that you can use slower EPROMS with faster a CPU. It gives the EPROM time to recover between memory accesses.
I am not positive that this is the reason for the split when used in an ECU, but that would be my guess.
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1991 SR20DET 180SX
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Calum
Joined: 11 Feb 2004
Posts: 227
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| Posted: Thu Jan 25, 2007 7:12 pm Post subject: |
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| Oggie wrote: | Odd and even arrangement is as you surmised - the odd numbered addresses go in one EPROM, then even numbered in the other. Typically this is used so that you can use slower EPROMS with faster a CPU. It gives the EPROM time to recover between memory accesses.
I am not positive that this is the reason for the split when used in an ECU, but that would be my guess. |
Nope. Right idea, wrong reason. The ecu is expecting 16-bit memory, but the common rom chips are 8-bit. So two chips are used (8+8=16). One chip supplies the lower 8-bits (even) and the other the upper (odd). Daughterboards that are burned straight up (i.e. both chips with the same data) just use a rom chip twice the size needed, and half of the chip is never actually used. |
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hottroc
Joined: 14 Mar 2005
Posts: 113
Location: UK
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| Posted: Thu Jan 25, 2007 11:13 pm Post subject: |
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Yes but I still don't get it... why not just use 16-bit rom chips? Nowadays they are easier to get hold of than 8-bit and any price difference is insignificant. Then you just need one instead of 2. And you can ditch the compllicated extra bits needed to make the odd/even function work.
Please correct me if I'm wrong, I'm a relative beginner.
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Calum
Joined: 11 Feb 2004
Posts: 227
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| Posted: Fri Jan 26, 2007 2:40 pm Post subject: |
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-8bit chips really are still cheaper
-2 28-pin ZIF sockets are cheaper than 1 40-pin zif socket
-there is better support for 8-bit chips in the low cost rom burner market
-if the daughterboard is setup for straight-up configuration its just as easy to use, and its still a simple design |
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V8MeatHead
Joined: 18 Jul 2005
Posts: 10
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| Posted: Sat May 05, 2007 12:39 am Post subject: |
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| Calum wrote: | -8bit chips really are still cheaper
-2 28-pin ZIF sockets are cheaper than 1 40-pin zif socket
-there is better support for 8-bit chips in the low cost rom burner market
-if the daughterboard is setup for straight-up configuration its just as easy to use, and its still a simple design |
excellent explanation Calum. Thank you! |
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raddy
Joined: 29 Nov 2005
Posts: 95
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| Posted: Sat Oct 27, 2007 10:28 am Post subject: |
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Hi
I need little help about reading odd/even files into the binary editor. Can you recommend me some editor which can join these files together to make it readible for Live Edit?
Thanks |
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