The parallel transfer cable

The parallel transfer cable was designed by Macro Vieth. The cable is used to connect a CPC/CPC+ or KC Compact to a PC to transfer data between the two systems.

The cable can transfer data in both directions. Transfer from the CPC to the PC is faster than from the PC to the CPC. This restriction is due to the limited number of inputs on the Amstrad CPC parallel port.

What you need

CPC with edge connector:

German CPC with Centronics connector:

CPC+ or KC Compact:

DescriptionMaplins Reference
34-way edge connector socket (female)FS80B
25-way 25-way D-Type plug (male)JW79L
36-way Centronics plug (male)FJ62S
34-way ribbon cableXR76H

Connections

PC parallelAmstrad parallel
2 (D0)11 (BUSY)
10 (ACK)8 (D6)
11 (BUSY)1 (/STROBE)
12 (PAPER END)7 (D5)
13 (SELECT)6 (D4)
15 (/ERROR)5 (D3)
19 (GND)19 (GND)

Reference

Algorithm for transfer from CPC to PC

Signals used:

Amstrad parallelData DirectionPC parallelFunction
8 (D6)>>10 (ACK)Data
7 (D5)>>12 (PAPER END)Data
6 (D4)>>13 (SELECT)Data
5 (D3)>>15 (/ERROR)Data
1 (/STROBE)>>11 (BUSY)Control
11 (BUSY)<<2 (D0)Control

D3,D4,D5,D6 specify the 4-bit data to transfer. /STROBE will be set low to signal a bit of data is ready. PC will set the BUSY to acknowledge the received data.

Algorithm for transfer from PC to CPC

Signals used:

PC parallelData DirectionAmstrad parallelFunction
2 (D0)>>11 (BUSY)Data
11 (BUSY)<<1 (/STROBE)Control

/STROBE is used to signal to the PC that the CPC is ready to receive data.

the PC will output data to D0 and will be read by the CPC on D0.

PC parallel port pin assignments

PinSignalDirection (SPP mode)
1/STROBEOutput
2D0Output
3D1Output
4D2Output
5D3Output
6D4Output
7D5Output
8D6Output
9D7Output
10/ACKInput
11BUSYInput
12PAPER ENDInput
13SELECTInput
14/AUTOFEEDXTOutput
15/ERRORInput
16/INITOutput
17/SELECT INOutput
18-25GND-

NOTES:

Amstrad CPC & CPC+ parallel port pin assignments

Pin Function Input/Output
1 /STROBE Output
2 D0 Output
3 D1 Output
4 D2 Output
5 D3 Output
6 D4 Output
7 D5 Output
8 D6 Output
9 D7 Output
10 N.C. -
11 BUSY Input
12 N.C. -
13 N.C. -
14 GND -
15 N.C. -
16 N.C. -
17 N.C. -
18 N.C. -
19 GND -
20 GND -
21 GND -
22 GND -
23 GND -
24 GND -
25 GND -
26 GND -
27 GND -
28 GND -
29 N.C. -
30 N.C. -
31 N.C. -
32 N.C. -
33 GND -
34 N.C. -
35 N.C. -

Notes: