Electronics > Repair
What more i can do?
222Lab_Test222:
--- Quote from: m k on January 06, 2025, 05:24:26 pm ---
--- Quote from: 222Lab_Test222 on January 06, 2025, 01:17:39 pm ---Looks like i need to again start from zero BUT keeping all the infos i get in mind.
--- End quote ---
No, you just change the mode for a moment.
Your ROM data measurements indicate that the CPU has no ROM access at all.
CPU is socketed and ROMs also, the environment of use is possibly hostile.
It's an educated guess that some socket contacts are or have been bad and have possibly taken some logic gates with them.
Diagnosing that is difficult without proper tools.
So the short cut is to change all easy targets, changing few bits too much is not an issue.
But first you must check how common problem this no ROM access is.
--- End quote ---
There is IC between CPU and ROM, does that somehow indicates the IC is the problem?
asis:
Hi,
The problem may not be in IC11; IC12, but in what it is controlled by (pin's: 1,19).
Only they determine the directions of request/service ROM,FRAM,DIM, etc.
For this reason, I ask to check the connections (CPU)IC8: P1, L3, D1,F3 on (74LS245)IC11: 11,18 (&) IC12: 11,18.
This will allow us to check whether we are developing correctly.
m k:
--- Quote from: 222Lab_Test222 on January 07, 2025, 02:21:28 am ---There is IC between CPU and ROM, does that somehow indicates the IC is the problem?
--- End quote ---
Rope has two ends, so either way.
Those low address CPU signals, combined with logic chips, are the thing for one direction.
There are also possible middle chips for other direction.
That is why you must measure same thing from different locations.
There are also possible connection problems, like inadequate socket contact.
That can be also so that multimeter measurement is fine, but live situation is not.
So ROM data you must measure from CPU pins, but its control, like address, from ROM pins, first.
If it's fine then fine, if not then you check the other end.
asis:
@mk
Let's first define what is connected with what and check it.
Only after that we will take measurements.
-
We have already gone through 547 different proposals, but the productivity from this is negligible.
m k:
Power, reset, boot.
I don't understand how that took so long, even without the actual code, it must still jump before address flips.
But I still don't know either how those data measurements are done exactly.
So maybe better do something possible advancing before next 500 replies.
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