write53775$D20FSKCTLSerial Port ControlSSKCTLall
read53775$D20FSKSTATSerial Port StatusSSKCTLall


0Enable keyboard debounce circuits.
1Enable keyboard scanning circuit.
2Fast pot scan: the pot scan counter completes its sequence in two TV line times instead of one frame time (228 scan lines). Not as accurate as the normal pot scan, however.
3Serial output is transmitted as a two-tone signal rather than a logic true/false. POKEY two-tone mode.
4,5,6Serial port mode control used to set the bi-directional clock lines so that you can either receive external clock data or provide clock data to external devices (see the Hardware Manual, p. II.27). There are two pins on the serial port for Clock IN and Clock OUT data. See the OS User's Manual, p. 133.
7Force break (serial output to zero)


0not used by SKSTAT
1Serial input shift register busy
2the last key is still pressed
3the SHIFT key is pressed
4Data can be read directly from the serial input port, ignoring the shift register.
5Keyboard over-run. Reset BITs 7 to 5 (latches) to one writing any number to SKREST at 53770 ($D20A).
6Serial data input over-run. Reset latches as above.
7Serial data input frame error caused by missing or extra bits. Reset latches as above.

see also: Keyboard topics

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