PDA

View Full Version : Checksum to clear 53 code



mock_glh
12-06-2007, 02:32 AM
From what I hear and read, D-cal will clear a 53 code with "checksum on save". What do I put in the "checksum address" box? I tried saving without anything entered in the address box and I still got the code.

I would also like to be able to put my own signature on my cals but the ones I tried this with didn't start. What's the trick? :confused2:

mw6886
12-06-2007, 09:30 AM
The checksum can be a little tricky to get to work in DCal for the LMs, but works pretty well in the SMEC/SBECs. I just do my checksums by hand.

If you are going to put a signature on your cals, the best place I have found is at the very bottom of the code, where there is usually a lot of space. I put other routines, extra code, remarks, whatever there.

mock_glh
12-06-2007, 12:17 PM
What is the purpose of the checksum anyway. My cals always run with the 53 code.

I've tried doing a signature down at the bottom as you describe, replacing the existing one, but the car doesn't start when I do it. Does it have to have a specific number of characters to run?

ShelGame
12-06-2007, 04:15 PM
Did you overwrite the interrupt vectors? That would certainly cause a no-start. Otherwise, it should be fine...

mock_glh
12-06-2007, 06:13 PM
Did you overwrite the interrupt vectors? That would certainly cause a no-start. Otherwise, it should be fine...

Huhh??:confused2: What are the interrupt vectors?

ShelGame
12-07-2007, 09:07 AM
In the SMEC, FFD6-FFFF are the interrupt vectors. When the computer starts up or certain outside events happen, these are the addresses where the computer starts executing code. As long as you don't overwrite these, you should be OK. But, if your sig over wrote these bytes, that's certainly why you got a no-start.

mock_glh
12-07-2007, 12:17 PM
In the SMEC, FFD6-FFFF are the interrupt vectors. When the computer starts up or certain outside events happen, these are the addresses where the computer starts executing code. As long as you don't overwrite these, you should be OK. But, if your sig over wrote these bytes, that's certainly why you got a no-start.

You mean 3FD6-3FFF. Those are in the last 3 rows of the program. I only meant to overwrite "CORP" and "J.R." but yes, I did do that. What about LM programs? Is it just the last row, 3FF0-3FFF?

ShelGame
12-07-2007, 03:02 PM
It's only 3FD6-3FFF until you offset it correctly. In the program space, it's FFD6-FFFF.

On the LM, the vectors are from FFF0-FFFF.

If you overwrote that space, then that's why you got a no-start. Just move your sig to earlier in the unused memory space...