ZX Spectrum Plus3 Aux

From HwB

Todo: This page needs some editing.

The AUX (auxiliary interface) socket supports two input lines (pins 2 and 5) and two output lines (pins 2 and 4). The I/O lines are driven by 1488 and 1489 line driver chips which are, in turn, connected to the I/O lines of the AY-3-8912 (see the manufacturer's data sheet for this device). Basically, register 16 of the AY-3-8912 controls eight I/O lines, the bits are designated as follows...

Bit Name
0 AUX pin 2 (out)
1 AUX pin 4 (out)
2 RS232 pin 5 (CTS out)
3 RS232 pin 3 (RXD out)
4 AUX pin 3 (in)
5 AUX pin 5 (in)
6 RS232 pin 4 (DTR in)
7 RS232 pin 5 (TXD in)

Using software control loops, the I/O lines could be driven as a second RS232 port (in the same way as the RS232/MIDI socket is driven using bits 2, 3, 6 and 7). Alternatively, the I/O lines could be used to drive, for example, a robot or some other external device.

    ___________________________
 __|   6   5   4   3   2   1   |
|__   ### ### ### ### ### ###  |
   |___________________________|

            AUX socket
Pin Function
1 GND
2 OUTPUT BIT 0
3 INPUT BIT 4
4 OUTPUT BIT 1
5 INPUT BIT 5
6 +12V

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