Nascom 2 keyboard connector

[Jules Richardson]

On Thu, 2005-06-02 at 23:36 +0100, Tony Duell wrote:
> > 
> > 
> > Does anyone have the pinouts of the Nascom 2 keyboard connector handy? 
> 
> Yes. I have the Nascom 2 manual in front of me. From waht I can see, the 
> keybaord came as an assembled unit, and there's no schematic in the 
> manual for that. But the pinouts of the connector are there, here you are 
> : 
> 
> PL3 (Keyboard) 
> 1 D0 (this is an input to a tri-state buffer, then onto the Z80 data bus)
> 2 +5V
> 3 D1
> 4 NMISw/
> 5 D2
> 6 Q5 (this is an output from a latch chip)
> 7 D3
> 8 Q2
> 9 D4
> 10 ResetSw/
> 11 D5
> 12 Q0
> 13 D6
> 14 Q1
> 15 D7
> 16 Gnd

One oddity with the IDC header on the keyboard PCB itself - it's not
numbered in a conventional fashion; pin numbering according to the PCB
run from 1-8 down one side and then 9-16 back down the other side (i.e.
same as a 16 pin IC). Meanwhile the CPU board keyboard connector (and
corresponding schematic) is numbered in a more conventional pattern with
odd pins on one side and even on the other.

> There is no description of the keyboard interface in the manual, and I 
> don't feel like battling through the monitor source lising to work out 
> how it works. Maybe the Q lines are decoded and used to scan the key 
> matrix in software or something.

Well the Nascom 2 keyboard seems to be very similar to the Nascom 1,
except that (as others have noted) it has an extra scan row so uses 7
data bits rather than 6.

Otherwise the signals seem to be the same, except:

  1) VCC is only on pin 16, not 15 and 16 as with the Nascom 1.

  2) Pin 8 on the keyboard PCB connects simply to a resistor, the other
end of which is connected to VCC. I assume it's supposed to connect to
DB7 on the CPU's data bus and allow detection in software of whether a
keyboard's present or not...

In all it uses 13 out of the 16 pins on the keyboard PCB. Pins between
the keyboard and CPU board *do* match up 1-1, it's just a case of
ignoring completely the pin numbering on the keyboard PCB!

cheers

Jules