turbo944

http://www.frwilk.com/944dme/88_to_86.htm

I found this as apparently in a bonehead move I ordered the 24 pin chip for a friend of mine instead of the 28. This seems to indicate that he's good to go, but it doesn't mention about going back if you need to cut the jumper or not so that the computer will use its own memory since all of it is not stored on the EPROM.

Can anybody shed some light on this for me?

Thanks!

TonyG

FRWilk is real up on these DME's.

I'd follow his instruction.

But if it helps, I've got a good '86 DME that I could swap you if you want (24 pin).

Eitherway, you can use the chip you have ordered for your buddy.

TonyG

turbo944

Awesome Tony. The only big question I have is that he doesn't mention on his site if you need to cut the jumper that tells it to ignore the internal memory of the 8051 that the 88 ones should have. It may not even matter, but otherwise it might cause it to only use 1/2 of its memory? Not big on electronic components knowledge here.... I did email FRWilk to ask him, but my firend is hoping to get it started today and if all we need to do is to plug it in, he'll be thrilled.

Thanks

TonyG

turbo944

If you read what is said about the jumper, you'll see that the jumper is added, so that you can add the 4 pins necessary to run a 28 pin chip on a board that was designed to run a 24 pin chip.


The jumper was added to control (or rather the instruct it to ignore) the additional memory that was provided with the other 4 pins (to the larger chip).

But since you are doing the REVERSE, you do not have to do anything.

You can simply install your 24 pin chip in the 28 pin socket as shown.

The existing jumper will have no affect on your chip since your chip does not have the extra 4 pins (the extra memory).


So look closely at the orientation and position of the 24 pin chip in the 28 pin socket.

Do that exactly.

TonyG

turbo944

Excellent!!!! Thanks Tony! That's great.

No problem on the orientation....we figured that out pretty quick based on the FRWilk stuff and how they normally go in

Danno

"You can simply install your 24 pin chip in the 28 pin socket as shown.

The existing jumper will have no affect on your chip since your chip does not have the extra 4 pins (the extra memory)."

You can try it, but it won't work because the CPU will be looking for the program on a non-existing portion of the chips. There are two parts to making the DME work, program-code and data. In the early DMEs, '86-87, the 4kb of program-code was located on the CPU chip and 4kb of data (fuel & ignition maps) was located on the removeable chip. In the later '88+ DMEs, the program-code was moved to the chips (data remained the same). This allowed for quick program-code changes without having to yank the CPU.

The 4 extra pins, Vpp, Vcc, A12, PGM allows for the extra addressing and this means the power line was moved to pin 28. If you put a 24-pin chip into a 28-pin DME, it gets no power. You have to do the reverse of the FR.Wilk mod (24->28p) that is, 28->24pin. You need to move jumper B700 to B707 because pin-31 is the ExternalAccess line on the CPU. On 28-pin DMEs, it's looking to the chip for its program code. You un-ground Vcc so that the CPU will use its internal ROM instead. It's kinda like booting your PC from an internal HD or an external one.

The table on the FR Wilk site seems to imply that the later '88+ cars do not have any internal memory in the CPU. So ALL of the program-code and data to run the DME is only contained in the 28-pin chips. Since the 24-pin chips only contains data and relies on the CPU to have its own on-board memory with the program, where does a 28-pin DME get its program code from when a 24-pin chip is used?

BTW- there are differences between the 28-pin 944 DME# 944.618.121.05 vs. the 28-pin 951 DME# 951.618.121.02

superjet.1

ok let me get this straight. the late 28 pin board comes stock with a jumper? so cut the jumper install 24 pin chip as directed and all is good.what about the klr is it the same?or do all klr have 24 pin

turbo944

So either way it won't work Danno? Does that mean your chips for the early cars and later cars are very different with the info stored on them? Or if the boards are very similar, would that mean that perhaps they left the code in the chip on the board and just ignored it because the information was also in the removable chip? Will those changes work well for it or would it just be better to get the 28-pin chip for him?

Would this cause any problem if he tries to start the car?

If this isn't going to work well, Danno, I'll get the 24-pin chip from him and ship it back to you first thing Monday if you can get him a 28-pin chip ready (this is the guy with the K27-8 that you made the map for with the Autothority MAF) and on its way. I don't mind paying the shipping on the new one you send as somewhere along the way I apparently messed up and told you the wrong one to send. Doh!!!!!!

Danno

Ok, I'll get you a 28-pin chip instead. The mappings on the 24-pin APE MAF chip is completely different than the 28pin version.

turbo944

Okay...thanks Danno!!!! I'll pick up the 24-pin and have it back in the mail to you Monday. I'll give him a call and let him know.

Wish my pump was here so I could get the car back in one piece and drive it....decent driving weather here today....can't wait to try out those Guru chips in my car hehehe