pcmhacking.net

Im a bit skeptical about the read... it doesnt seem to work out whatever way I try it.

So I went back and checked my notes, and found this... its a VN L3 dash so it may be different, but its the same cat chip, and the same layout board. I have worked out this much:

300,609
Its binary coded in to nibbles, with the opposite endian layout to x86 so to make life easier heres a MSB/LSB nibbles look up chart
so solve the endian part and convert to BCD: 300,609 = C0 06 09 = 0C 60 90

One of the sums is stored right next to each byte so then you find:

F30C 9F60 6F90

if it helps here's the list of chips support by the 4x i use.

http://www.mcumall.com/comersus/store/m ... ortICs.asp

antus wrote:So I went back and checked my notes, and found this... its a VN L3 dash so it may be different

My First one is from a vn the second from a vs. Both Boards looked the same to me, same chips, some different brands but still same chips, same layouts

Maybe the reads are reading ram without first loading the data backup up from e2prom which is why we see not the right content yet it still works when resoldered.

festy wrote:

VL400 wrote:Both of my programmers dont support it So would need to be a pic/avr to read it like festy suggested. Would be interesting to get the MCU code out too

A Willem PCB3 clone should be able to read and write the 24C44 using software version 0.97ja, select "S24H45" for the device.
Or here's an ebay ICSP programmer for $20 that will do them too.

just had a look at that ebay one, it does'nt have 24c44 or S24H45 listed either.

X2444 is compatible from what i've read.

festy wrote:X2444 is compatible from what i've read.

arh yes it does. Well $19 ill give it a go, let you all kow when i get it.

If you had an old dos machine around, your could try this...

antus wrote:

Code: Select all

>From address: 000000  To address: 000087   Date: 2/12/2007  Time: 5:53:22 PM

Address      +0    +1    +2    +3    +4    +5    +6    +7    0 1 2 3 4 5 6 7
-------------------------------------------------------------------------
00000000   0101  D926  FF00  DF20  FC03  F30C  9F60  6F90   ..&. ..`o
00000008   FC03  F30C  9F60  6F90  FC03  F30C  9F60  6F90   ..`o..`o

One of the sums is stored right next to each byte so then you find:

F30C 9F60 6F90

I'd been through packed BCD etc in the two samples and couldn't see any pattern, but your data makes much more sense.
So the second checksum is 90^60^0C^FF = 03, and it's partner checksum of 03^FF = FC, making FC03?

(edit - second checksum would be XOR'd, not addition)

antus wrote:Im a bit skeptical about the read... it doesnt seem to work out whatever way I try it.

Well I think the data The1 read must be invalid, i just looked up the READ instructions for the two chips and can see why it didn't work:

24c44: 1AAAA11X
93c46: 10AAAAAAAA

So although the eprom programmer hardware is capable of talking to the 24c44, the software doesn't support the instructions.
If the source code was available it would probably be trivial to add support for it.