View Full Version : Burning M27C256B

08-18-2006, 11:04 PM
Alright. I have no idea what I'm doing wrong here, but maybe someone can help. :confused: What are the VPP and VCC settings I should use for burning an M27C256B in an '91 SBEC? Is there any other settings I should know about before I try this again, like offset or anything? I think my chips are fried, but I dont know.


08-19-2006, 12:14 AM
What burner are you using? The 27 series stuff is pretty forgiving about timing issues. Are they erased?

08-19-2006, 01:15 AM
Yeah, I'm sure they are erased. I must have erased them about 10 times today trying to figure this thing out :yuck: I'm using the Willem Dual Power burner... I have tried using both USB and AC power.

08-19-2006, 01:29 AM
Can you read them and when you do is the buffer all FFs?

08-19-2006, 01:37 AM
I recall seeing FF's there, but the computer I have to use for burning chips is at my neighbours, and its late right now. :( Ours is too new to have the old style "printer" port.

When I go to write on a blank chip with all normal jumper settings, normal DIP switches, all Normal settings I guess, and use all the settings that are on the 0.97G program when you select the M27C256 chip.

I can blank check the chip, it will be empty, then when I program, it says it programs and verifies ok, then I blank check and the blank check fails, and I then I think I have it right. Then I go home, put the chip in the SBEC, put it in the car, and whammy, nothing works. As soon as I connect the battery, the left front signal light flashes for a second for some reason, and thats about all that happens. Then it just cranks over with nothing, the A/F gauge lights going crazy, etc.

08-19-2006, 01:53 AM
OK, so you aren't sure that it isn't being programmed necessarily...just that when you do the the car doesn't start. Does the module boot (does the CEL come on when you turn on the ignition)?

08-19-2006, 02:45 AM
That's the wrong chip for an SBEC.. SBEC's use 87c257's, not 27c256's like the SMEC's and LM's used..

08-19-2006, 02:53 AM
Actually they used 27C128s (which are extinct), but you're right.

08-19-2006, 03:06 AM
Actually they used 27C128s (which are extinct), but you're right.
What did? '88 SMEC's? Yes.. '89 SMEC's used 27c256's.. And LM's used 2764's originally, then moved up to 27128's.. No C meaning they were N-MOS rather than C-MOS.. But still compatible with C-MOS obviously..

08-19-2006, 03:53 AM
Well, if you want to split hairs, the 84s used bipolar PROMs! Anyway, I've seen 87 LMs with 27128s and 27C128s.

I finally installed Windows 98 on my laptop so that I can program 28 and 29 series stuff again. My old EMP-10 is a "dumb" parallel port programmer whose software can't generate tight enough timings on a real OS. Programmed the crusty old 27 series stuff just fine, but the wait in the eraser (or forgetting it was on and giving the chips a week-long sun tan) was annoying.

08-19-2006, 01:59 PM
Ok, so the M27C256's won't work in the SBEC? Where can I get a chip that will work?

And no, the check engine light wasn't even turning on.

08-19-2006, 02:01 PM
87C257 - Mouser.com, $5.99/ea

08-19-2006, 03:30 PM
hehe, $6 a pop.. I always desolder the SBEC's very carefully and save that chip. The extra time is worth it to me.. (Especially if you've seen mouser's shipping charges)