udisk - universal disk controller for UNIBUS - async cpld timing

Async CPLD

My first attempt at controlling and responding to the UNIBUS was via a simple "async" cpld. No clock, just raw logic inside a CPLD. I wanted to do as much as possible via software and see how far I could get.

I found that I could get things to work, almost, but not as fast as I wanted. Still, I got RT11 to boot.

Here's the verilog; very rough, just a prototype with a simple test bench.

• udisk_cpld.v
• udisk_test.v

Here are some pictures from my HP1650A, taken from signals on the udisk board. Sorry for the crooked images; they are scans of printouts of screenshots.

Below are:

• unibus repeating read
• unibus at rest
• pdp-11 simple code loop
• unibus 4 word dma
• unibus npr/npg
• unibus br5/bg5 + sack

unibus repeating read

unibus at rest

pdp-11 simple code loop

unibus 4 word dma

unibus npr/npg

unibus br5/bg5 + sack