Here are the signals on the cable:
Pin 1 - Ground Pin 2 - Ground Pin 3 +5 volts Pin 4 -12 volts Pin 5 D0 Pin 6 D2 Pin 7 D4 Pin 8 D6 Pin 9 read - 2E2 Pin 10 write - 2E0 Pin 11 +5 volts Pin 12 - Ground Pin 13 - Ground Pin 14 - Ground Pin 15 +5 volts Pin 16 +12 volts Pin 17 reset Pin 18 D1 Pin 19 D3 Pin 20 D5 Pin 21 D7 Pin 22 write - 2E2 Pin 23 +12 volts Pin 24 +5 volts Pin 25 - GroundSo we have power, ground, and 8 bit data bus, reset, and 3 control signals.
The control signals are designated for one base address (namely 2E0), but in the general case they would be BASE + 0 and BASE +2.
We are getting ahead of ourselves, but things work as follows:
Call 2E0 the "ID port"
Call 2E2 the "data port"
The control signals are active low. So when you write to port 2E0, the signal on pin 10 goes low. Similarly when you read from port 2E2 on the ISA bus, the signal on pin 9 goes low.
The ID port selects various registers inside of the EMUP, but all of this is a subject for a different page.
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