Analogue-sequencer

> I have more info now.  The RS, R/W, and CE signals for the display
> only output 3us pulses.  According to the PLED datasheet they should
> remain high/low for the duration of the read/write.  Also, only
> DB0-DB2 show any activity.  Any ideas?  Thanks

The communication between the CPU and PLED module amounts to:
"wait for the LCD to be ready"
"read/write to/from the selected register"

If the module is disconnected or bad, the CPU can wait forever for it to be
"ready", and will not appear to boot.
The "ready" bit is DB7.
Zero is ready, one is busy.
You can fool the CPU into thinking it has a working PLED attached by
connecting pin 14 of the LCD interface (DB7) to pin 1 (ground).
If that doesn't make it boot and flash its LEDs, you could have a problem
with the main PCB or the code on the CPU.

Best regards,
Colin Fraser
Sequentix Music Systems Ltd
http://www.sequentix.com