cable being connected so that pin 1 of PL4 is connected to pin 1
of the D-type. The 26th cable, from PL4 pin 26 is not connected,
since it carries no signal from PL4. This is the cable/connector
combination fitted as standard on the Nascom 3.
This leads to a rather arbitrary arrangement of the port
lines at the D-type, but does mean that add-ons designed to
connect direct to PL4 can still be easily connected merely by
fitting a Scotchflex D-type plug in place of the header plug.
The resultant allocation of pins is as follows, colours refering
to multicolour Scotchflex cable (where grey cable is used the
marked line should be connected to pin 1);
PL4
Pin
| D-type
Socket | PIO
Function | Colour | Parallel
Printer |
|---|
| 1 | 1 | B5 | Brown | 7 |
| 2 | 14 | B4 | Red | 6 |
| 3 | 2 | B6 | Orange | 8 |
| 4 | 15 | B3 | Yellow | 5 |
| 5 | 3 | B7 | Green | 9 |
| 6 | 6 | B2 | Blue | 4 |
| 7 | 4 | ARDY | Violet | |
| 8 | 17 | B1 | Grey | 3 |
| 9 | 5 | BSTB | White | |
| 10 | 18 | B0 | Black | 2 |
| 11 | 6 | ASTB | Brown | |
| 12 | 19 | BRDY | Red | |
| 13 | 7 | A0 | Orange | 11 |
| 14 | 20 | No con. | Yellow | |
| 15 | 8 | A1 | Green | 1 |
| 16 | 21 | GND | Blue | 14 |
| 17 | 9 | A2 | Violet | |
| 18 | 22 | GND | Grey | |
| 19 | 10 | A3 | White | |
| 20 | 23 | +5V | Black | |
| 21 | 11 | A4 | Brown | |
| 22 | 24 | +5V | Red | |
| 23 | 12 | A5 | Orange | |
| 24 | 25 | A7 | Yellow | |
| 25 | 13 | A6 | Green | |
| 26 | | No con. | Blue | |
6. The Advanced Video Controller (AVC)
Next issue we hope to include, space permitting, the first
part of an
article on the AVC
by Peter Horton, who designed the
card and wrote most of the support software. We will
continue this article
next month. In a future issue we will be describing
how to make use of animation with the AVC.