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Old/Junque Memcals needed


padgett
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I need a couple of memcal carriers for my E-Prom reprogramming project if anyone has some - can be stock or whatever, PROM can be good or bad, just need the carrier and auxilliary stuff.<P>Have all of the necessary equipment now, just do not feel comfortable digging into mine until have dissected a few cadavers.<P>Would not turn down whole ECM/BCM working/nonworking or two if the price is cheap. (Really need to go out junquing as soon as the weather cools off a bit more).

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Whole 'nother world out there... <A HREF="http://www.thirdgen.org/newdesign/tech/promintro.shtml" TARGET=_blank>http://www.thirdgen.org/newdesign/tech/promintro.shtml</A> <P>Actually disassembled my first CCC back in 82 or 83 (on a VAX) but have been out of it for a while.<P>Purpose at moment is simple: reprogram the coolant fans so they switch to HI at 200F and back to LO at 190. Preliminary research indicates I only need to change three bytes and think I know which. <P>As long as am doing that might as well update to latest PROM for '88 (p/n 16123488 that came out as a slipstreamed change for the '88 in mid '89).<P>Once I get that done, will go deeper but even to do same for other years (88-90 all used the same 1228253 ECM but each had a different PROM) would first need a sample (or a hex dump of the contents).<P>Next will attack the BCM but there is very little information on that whereas the 27C256 PROM/P4 has already been extensively mapped by the GN crowd.<P>Bottom line: have most of the equipment already (just dusted off Prom burner and can R/W 256s) and would rather spend $5 for a PROM that does what I want rather than $100 for one that doesn't.<P>However, to get back up to speed I need some samples for "destructive testing" and thought this crowd might be a good place to troll. $40/each (with shipping) from Flow is a bit dear. <P>Besides I hate to do any experimenting without a spare available for when Murphy strikes.<P>Of course this will probably take a while, summer is about over and my travelling is starting again and I have all these rear camber shims to sort out...<p>[ 09-21-2001: Message edited by: padgett ]

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For the regular challenged, Padgett wishes to program his own PROM for his ECM, Engine Control Module. This is the silver computer by the glove box that controls engine functions. Each ECM will have a multipin caterpillar looking IC, Integrated Circuit, that unplugs from the circuit board. The PROM is programed by the manufacturer and contains data to adjust fuel, timing on the engine with inputs such as throttle position, RPM, temperature, etc.<P>The PROM is erasable with special equipment. Padgett wishes to erase extra PROM's and reprogram them to his liking. Perhaps he wants more speed. Or more performance.<P>This is truly geek stuff and takes someone that is fasinated by computer programming or software. And we know how software types are! This is what they like and enjoy.<P>Padgett is thus looking for extra PROM's and socket assemblies and complete ECM's.<P>Hope I said it right. Hardware Russ. grin.gif" border="0

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Guest cdoersom

I too am interested in reprogramming the ECM (to change the temp. settings) and also to learn more about the touch screen computer. I too did assembly language programming in the 80's and am a bit rusty but can get up to speed with a little work. I have a prom burner and an eraser too.<P>What do you know about the touch screen? What model computer chip runs it and where is it located? Is the prom in a carrier like the ECM, or socketed, or soldered in place? <P>Thanks,<BR>Chuck cdoersom@swbell.net

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The mileage is stored in the BCM, not ECM PROM. Messing with this stuff is illegal. It is just about impossible to obtain a replacement PROM for the BCM from GM. A lot of legal paperwork needs to be done along with a return of the existing PROM before a new one will be burned in and issued. That's why the VIN is part of the BCM PROM. That's why it is important to read the VIN on the diagnostics of any Reatta before purchase to check for mileage fraud. frown.gif" border="0

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Have now dumped the 16123488 "ANCX" PROM ('88 replacement) to a file and am starting to pull apart. Tricky part was making an adapter to mount the Memcall in the programmer<P>Looks like the 32kbytes (256kbits) is split in half with the data elements in the first 16k (just using about 5k) and the program is in the second 16k.<P>Problem is that the layout does not match any of the maps I have seen so will require some more sophisticated tools (going to have to dredge up the disassembler).<P>If anyone is interested in the dump (32k file), I can E-mail.<p>[ 09-22-2001: Message edited by: padgett ]

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Guest cdoersom

padgett,<P>The last 16 or so bytes of the prom are a jump table which should point to the starting point (which I think are the last 2 bytes - in mine, an 89 orignal prom ASSU, it's $B05A). I am interested in a copy of your prom dump to compare to mine. Thanks,<P>Chuck cdoersom@swbell.net

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Yes, common trick for computers (PDP-8 was the first I saw like that). IBM-PC does the same thing (the BIOS is always at segment F000 - PC initializes the IC at FFFF:0000 and executes what ever is there at startup.<P>Is why the 32k 27C256 is addressed between 8000h and FFFFh. Just think of it as a PC that only has the BIOS. The H11 does have a limited amount of RAM onboard.<P>Suspect when I pull apart a BCM that the EEPROM (VIN, odometer, checksum) will be located just under 8000h.

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RED REATTA RUSS,<BR>THANKS, for letting the rest of us know what Padgett is trying to do. Hay, he is my new friend and is the reason my old 88 is back up and running. I just need to get the cruise control back into service not change the mind of the G.M. programers.<BR> ken

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Ok we are dealing with two computers here and need to keep track of which does what.<P>ECM or engine control module started out as a Motorola 68C01 with some extras like onboard ram. These have been in virtually all GM cars since 1982.<P>The Reatta used the second generation of these called a P4 (specifically the 88-90 code "C" engine uses a 1228253. This is the same for *all* cars with 3800 "C", not just the Reatta.<P>The P4 has an ALDL (assembly line data link) rate of 8192 bps (think of it as modem with a really strange speed). <P>Both the program and the data maps are stored in a 27C256 UVPROM (27-UV, C-Cmos, 256- 256kbytes).<P>Note: GM cars rarely calculate values, rather everything from spark advance to cold enrichement is found in tables - for X rpm and Y gear and Z MAP set EST (electronic spark timing e.g. advance curve) to A degrees.<P>As the name implies, the ECM controls the engine. Later devices combined ECM, ETC (electronic transmission control), and ABS in a single module but the Reata was built before that.<P>As far as most GM cars are concerned, the only indication the driver sees of the ECM operation is the SES (service engine soon) light.<P>BCM - what sets the Reatta (and other touchscreen cars - Riviera, Toronado,...) apart is the Body Control/Computer Module. This is a completely sparate computer from the ECM though I *suspect* (have been promised a BCM to play with but has not arrived as yet) the BCM is a very similar platform to the ECM and would not be surprised to find the same 6800 based CPU as the ECM. Just do not know as yet.<P>The BCM takes a wide range of sensor inputs including those from the ALDL (on most cars you need a scan tool to access this information. The Reatta has a rudimentary one built in) and some from the occupants via the touchscreen. It uses that information to create the displays on the IPC (Instrument Panel Cluster) and the CRT (Cathode Ray Tube), tune the radio, and set the A/C.<P>The BCM also stores in non-volatile memory (does not go away when the battery is disconnected) information relating to VIN, and odometer reading. This information is protected with checksums to detect if tampering has taken place.<P>My first target is the ECM since my first concerns (cooling fan turn on/off settings and idle control (think 650 rpm is too low for a/c to function properly) are there and because there is already quite a bit of information on the ECM courtesy of the Grand National people who have been fiddling with GN (turbo 3800) ECMs for years. You can find a lot of information on the ECM at <A HREF="http://www.cruzers.com/~ludis/p4xref.html#1228253" TARGET=_blank>http://www.cruzers.com/~ludis/p4xref.html#1228253</A> .<P>Plan to go to the BCM next even though there is very little available information. Have not decided all I want to do but know I want to replace the odometer readout on the IPC with coolant temp and oil pressure - with the guage screen up you cannot do much.<P>Am hoping to do a bin dump of the 16123488 Memcal this afternoon for study. Suspect I will need to dredge up my 6800 disassember also.

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