| ADR | HEXADR | NAME | Description | OS |
|---|---|---|---|---|
| 54018 | $D302 | PACTL | Port A Control | all |
| Bit | Function | Description |
|---|---|---|
| 7 | PA7 | read only: Interrupt status of PROCEED, 1=Interrupt |
| 6 | PA6 | always 0 |
| 5 | PA5 | always 1 |
| 4 | PA4 | always 1 |
| 3 | PA3 | Cassette player motor control, 0=on, 1=off |
| 2 | PA2 | 1=use Port A for data input/output, 0=define data direction, see below |
| 1 | PA1 | always 0 |
| 0 | PA0 | Interrupt of PROCEED line on/off, set to 0 by OS |
To define the data direction of PORT A, set Bit 2 of PACTL to 0. Then write a byte to PORTA, where Bits set to 1 indicate WRITE and Bits set to 0 indicate READ. Normally PORTA set to %00000000 (=all input).
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