1227747 TBI Chip options currently available? AT28C64 anyone use them?

[kilohertz]

Starting to gather all the stuff for my Flathead TBI build this winter and am wondering what chips would work in place of the EPROMs. I know the 27SF512 is one but my programmer doesn't have the module for it, and it's obsolete. I see AT28C64 are still available...any other device options you can suggest? I am planning on a ZIF socket as I am SURE there will be a lot of changes to get this to run correctly on the flathead.

Cheers

[In-Tech]

https://www.jdr.com/SearchResults.asp?Search=2732a

[trlrider]

27SF512's are still readily available thru several sources. I purchase mine thru Moates to make sure I am not getting the chinese knockoffs.
I do not believe the AT2864 will work in the '7747. Remember reading sometime back about the reason, but lot's of water under the bridge since then.

[kilohertz]

ok thx for the replies.

As mentioned I don't want to use EPROMS as I will be making many changes...hence the eeprom or flash. Also as mentioned my programmer can't program the 27sf512...trying to work with what I have.

cheers

[dave w]

I posted this tread many years ago: http://gearhead-efi.com/Fuel-Injection/showthread.php?172-7747-Flash-Chip-Conversion-(27SF512) it's been helpful for several gearhead-efi members.

dave w

[joegreen]

Have you considered purchasing a burn 2 to program the 27SF512's?

[kilohertz]

I posted this tread many years ago: http://gearhead-efi.com/Fuel-Injection/showthread.php?172-7747-Flash-Chip-Conversion-(27SF512) it's been helpful for several gearhead-efi members.

dave w

Thanks for the reply Dave, I appreciate it. I have read many of your threads/posts and want to thank you for all of your work to help people here. I have read the thread you mentioned and am in the process of picking a EEPROM to use, I found today a few posts on the 3rd Gen Camaro forum where they had used the AT28C64 with similar pin joining on 1,2 and 27,28 as the 27SF512. For whatever reason, my EMP-20 programmer requires a different module than the one for the 27XXX and 28XXX series chips. I think even the 29C040 can be programmed with the same module I have. I could go online and try and find it, but highly unlikely.

I'll do some more research on the 28C64..they are only $8 so it's not a big deal to try one.

Cheers

[dave w]

ok thx for the replies.

As mentioned I don't want to use EPROMS as I will be making many changes...hence the eeprom or flash. Also as mentioned my programmer can't program the 27sf512...trying to work with what I have.

cheers

I'm very familiar with chip programming. I'm not familiar with the AT28C64 so I looked at Mouser for information: https://www.mouser.com/ProductDetail/Microchip-Technology-Atmel/AT28C64-15PC?qs=HAf9pce8hngKjb3SuxMz5Q%3D%3D and then looked at the data sheet: https://www.mouser.com/datasheet/2/268/doc0001-1180850.pdf

The 1227747 uses a 4K chip. The AT28C64 is a 64K chip just like the 27SF512 is a 64k chip. After reading the AT28C64 data sheet, it appears to me the AT29C64 can be used in the 1227747 with "Offset Programming" because only the bottom 4K memory of a 64K memory chip is needed for the 1227747. Additional information about programming with offsets can be found on the Moates.net website:http://support.moates.net/programming-chips-using-offsets/



Offsets for a 4k chip being programmed into a 64K chip
Microchip AT28C64
Buffer -> 000000 -> 000FFF or Hexadecimal for 4K chip memory size
Address -> 00F000 -> 00FFFF or Hexadecimal addresses to program only the bottom 4K addresses of a 64K chip

For example if you were going to program the AT28C64 for the second generation TBI computer 16197427 which uses a 64K chip no offset is needed.
Buffer -> 000000 -> 00FFFF or Hexadecimal for 64K chip memory size
Address -> 000000 -> 00FFFF or Hexadecimal addresses to program all addresses of a 64K chip

dave w

[kilohertz]

Awesome! Thanks Dave for the confirmation...4 chips on order and will be here before the weekend. This was supposed to be a winter project for me when there is no paid work... but I seemed to have jumped the gun...I can always clean the house next year. :laugh:

Cheers

[kilohertz]

The 1227747 uses a 4K chip. The AT28C64 is a 64K chip just like the 27SF512 is a 64k chip.

Correct me if I'm wrong, but the 1227747 uses a 2732 which is a 4Kx8 (32Kb) chip, the 28C64 is an 8Kx8 (64 Kb) chip, the SF512 is a 64 KB, being a 512Kb chip...I think. The big difference is the B vs the b, bits vs Bytes.



Offsets for a 4k chip being programmed into a 64K chip
Microchip AT28C64
Buffer -> 000000 -> 000FFF or Hexadecimal for 4K chip memory size
Address -> 00F000 -> 00FFFF or Hexadecimal addresses to program only the bottom 4K addresses of a 64K chip

For example if you were going to program the AT28C64 for the second generation TBI computer 16197427 which uses a 64K chip no offset is needed.
Buffer -> 000000 -> 00FFFF or Hexadecimal for 64K chip memory size
Address -> 000000 -> 00FFFF or Hexadecimal addresses to program all addresses of a 64K chip

dave w

Today, after spending a few hours figuring out how to use my 30 year old Needhams EMP-20 programmer, I successfully programmed the AT28C64B with buffer offsets 1000-1FFF, which should be the last 4K of the 8Kx8 space, the first 4K being 0000, 0FFF...I think. It's been years since I have done this stuff. I confirmed data in the chip matches the data in the buffer, but just offset to the last 4K of the 28C64. I built the 28P ZIF mod socket and soldered it onto the 747 board today, I won't know for a while if it works, but it should.

Thanks for the help.

Cheers

[dave w]

SST 27SF512 = 64K https://www.futurlec.com/Memory/SST27SF512.shtml

Often a less confusing technical description for chip size is written 64K instead of 64K x 8 or 4K instead of 4K x 8.

I have found the offsets shown on the Moates.net website (post 8) to be accurate.

dave w

[kilohertz]

It's been a few years but back in January 2022 I was able to get the Flathead Ford running perfectly with the 7747 using the AT28C64 chip. My programmer worked 100% and I ended up making 29 changes to the tables before getting it running nicely. I'm back working on the truck and making the final wiring harness.

Wanted to update this thread in case anyone else is looking for a chip option for the 7747.

Cheers