Model 100 Serial Interface

Configuration

Serial Word Format

Port $D8 controls the serial word format.

Bit	Function	Note
0	Stop bits	0 → 1 stop bit 1 → 2 or 1.5 stop bits (1.5 if character length is 5, 2 otherwise)
1	Parity	0 → Odd parity 1 → Even
2	Parity Inhibit	0 → Parity 1 → No parity
4-3	Character length	Number of bits: 00 → 5 01 → 6 10 → 7 11 → 8
7-5	Unused

I/O Map

Name	Direction	Port
TX	Output	$C8
RX	Input	$C8
RTS	Output	$BA, bit 7
CTS	Input	$BB, bit 4
DSR	Input	$BB, bit 5
DTR	Output	$BA, bit 6

Direction indicates both data flow, and whether to use an IN or OUT instruction to read/write to the given pin.