Tuesday, December 20, 2016

Construction progress on PCBs and cabling, plus more testing


Parts are on order to complete the remaining driver and emulator boards - shipped today but not likely to get here before Xmas due to the heavy volume at all the delivery services. I did put on some of the components I still had - capacitors, IDC connectors and driver chips, for instance - before putting the boards aside.

Testing out the new driver board involved checking a number of items, as listed in yesterday's post. Step 1 was already complete.  
  1. Verify that SelectUnit1 is switchable and not permanently on from the fpga
  2. Verify that the terminator has the pull up and pull down resistors installed for all the signal lines I am driving, but none on the lines returning from the Diablo to my fpga.
  3. Monitor signals incoming to the PCB to validate their correctness
  4. Monitor signals at the terminator when my PCB is driving the Diablo to validate their correctness.
Steps 2 and 3 were relatively straightforward, as there is easy access to the pins needed to monitor those circuits. Step 4 is more challenging and will require hooking on micrograbbers and multiple cycles of removing and installing the terminator. 

I found several of my incoming signals had termination on the sending end, as well as on my board. I clipped off the resistors on those signals. Everything else checked on with termination resistors, allowing me to complete step 2 above.

Step 3 will be done by a simple power up and attaching the scope probes to the tops of the three level shifter mini-boards across the top of my PCB. 

I took some time to put the IDC connector on the ribbon cable that attaches to the Alto disk controller card on its other end. This cable is now attached to the emulator board. 

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