Monday, January 11, 2016

Whittling down the suspect count

All I wanted to do as a first pass was to identify those that need a closer look and which don't. But since I don't have an index of which FETs are used for what purpose I had to take a look at all 105 FETs connected to Vdd to identify them. Searching for a FET by part identifier and recognizing one of the common configurations I listed in the previous post only took a few seconds per part.

It turns out there are eight tri-state drivers, reducing the number of suspect circuits from 20 to 12. Here's the list:
  • T0667 -- ACC D0 input latch precharge
  • T0668 -- ACC D1 input latch precharge
  • T0669 -- ACC D2 input latch precharge
  • T0670 -- ACC D3 input latch precharge
  • T0857 -- I/O D3 output(?) precharge
  • T0858 -- I/O D2 output(?) precharge
  • T0859 -- I/O D1 output(?) precharge
  • T0860 -- I/O D0 output(?) precharge
  • T1333 -- unknown
  • T1477 -- unknown
  • T1510 -- ALU D1 precharge
  • T1512 -- ALU D3 precharge
I recognized what some of these do from developing the Verilog implementation and I've noted as appropriate. Of course I'll still check the timing of these. I may even double-check the timing of the IP and SP column sense precharge FETs while I'm at it.

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