PDP-8 question...

From: ajp166 <ajp166_at_bellatlantic.net>
Date: Mon Oct 16 21:34:09 2000

-----Original Message-----


Mega thanks, that makes some sense looking at the board.
I'd suspected something like that. Te ability to start on any
4k boundary is nice. The 74138 on one side and the '20 on
the other should have screamed at me.

Allison

>The 16 pin DIP socket has a "black box" plugged into it. Hmm, popping
>that box open reveals the expected jumpers.
>
>Looking down at the jumpers, the upper left corner is pin 1, upper right
>is pin 16, I have 4 wires installed:
>
> pin 5 - pin 14
> pin 6 - pin 13
> pin 7 - pin 12
> pin 8 - pin 11
>
>My board is set to cover fields 4 - 7.
>
>My guess would be that the 3 EMA bits are decoded into 8 lines, and are
>present on pins 1 - 8, corresponding to DEC field terminology 0 - 7,
>which makes obvious sense since pins 1 - 8 are on one side of the
>DIP jumper, and that pins 11 - 14 are the individual 4Kx12 field
>select jumpers.
>
>-Lawrence LeMay
Received on Mon Oct 16 2000 - 21:34:09 BST