Unsuccessful gz_loading troubleshooting notes

So I started looking closely at Guzunty Pi #2.  This time I trace the TDO and TDI signals, because I remember that I had problem proving RPi JTAG TDI pin can read, though it can output.

I repeated a couple of times loading the same gz_test.xsvf file.  Everytime the waveforms look OK in the beginning, with TDI similar to TDO, but then both signals become short pulse trains, and the period between pulse trains get longer and longer, from perhaps under a second to over a couple of seconds.  I guess the load program is increasing the between trial periods after every TDO mismatching event.

I guess the the CPLD is some how working in the beginning, because TDI seems returning something to respond to TDO's commands.  I remember that if I switch off power, or no CPLD in socket, or JP1~4 wrongly set to RUN mode instead to PROGRAM mode, then the loading exit almost immediately.

It is at this point that I began suspicious perhaps the CPLD is faulty, or too slow to follow the gz_load commands.

So I decided to use another CPLD and try my luck again.

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