Analogue-sequencer

> so i'm looking at the assembly site... and on the function 
> board we've got
> a two-way header that connects to a four-way header on the 
> main board via
> a single wire... why is this? why not just a two-way to two-way
> connection?

There's just a single pin used on this connection - it was a late
addition to the P3 design.
It's an open-collector output that drives the LEDs on the function
switch board. The original LED matrix was only designed to support 32
LEDs (16 x 2 in tri-colour LEDs). When I decided to add dedicated
function select switches (they used to be soft-keys in pattern edit mode
only) I used one of the four spare TTL outputs on a 574 latch to drive
the extra row of LEDs.
The 4 pin connector is on the mainboard in case I ever think of
something to do with the other 3 outputs.
I might, for example, design a little board with a 7 segment LED on it
that will display P, L or E for the current mode, and lose the inverted
video characters from the PLED (optionally, of course).
There's a 2 pin connector on the function board because 1 pin connectors
don't stay connected very well.

Cheers,
Colin f