Monday, January 16, 2017

Doing some cleanup of logic and chasing temporary cable issue


Video of tool seeking to read cartridge in a single transaction

Disk tool ready for use
I did some cleanup on the testbed and the fpga logic and discovered a flaw in my disk driver tool functionality. I am working to resolve it, which shouldn't be too long because the flaw can't be too subtle or complex.

It appeared that I when wrote the disk image to the cartridge, I may have stuttered or repeated the second head information on both sides of the cartridge. Or, my reading is always looking on one head and disregarding the head signal.

I will try some experiments to manually read a sector, controlling the head signal. I also  put the scope on the head control signal going into the Diablo drive to observe whether it worked or did not. At the same time, I moved over to board 1 and my newly built PCB to Diablo cable. I verified connectivity and saw the head signal switching back and forth as it performed a ReadEntireCartridge.

With the extracted disk image file converted over to an archive format, I did a word for word comparison to the written image and had zero disagreements. This tells me that either board 2 is failing or its connector to the PCB to Diablo cable was loose. I will switch over to these and see how they perform.

Board 2 and its cable were reconnected and I attempted to read the disk again. I found that the ready status was intermittent and jumped around when I lightly touched the connector. I decided to remove and replace the connector on the cable.

In addition, I did some checkout of board 3, which I suspect was really the defective cable causing symptoms. I will put the rebuilt cable on board 3, verify its operation. I know that board 2 works properly when the cable is good. Alas, board 3 is NOT working properly.

I swapped the cable back to board 2 and tried one last time, since it was late at night. It still didn't work properly. I removed the new cable and rigorously checked each connection, which proved to be flawless. At this point, I don't know what is wrong but I will dig into this and figure it out.

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