F Unction Code 0 — Initialize The Serial I/O Port - Zenith Z-100 Reference Manual

page 8.8
Serial and Parallel Input/Output
Serial Port
The following operations are recognized using the serial interrupt, 14H. As before,
AH is loaded with the operation code corresponding to the desired function. DX
is loaded with the serial device designator, 0 or I, before the interrupt is executed.
Table 8.8 defines the operation codes recognized by the system when using the
serial interrupt
Table 8.8. Serial Device Operation Codes
CODE DES C RIPTION OF ACI'ION
Initialize the serial I/O port
Send character in AL to the serial port
Receive character in AL from serial port
Read communications status
The following paragraphs further define these serial device operations.
Function Code 0 — Initialize the Serial I/O Port
The mode of the selected port is determined by the bit-mapped value in AL
as shown in Table 8.9.
Table 8.9. Mode Select Byte Breakdown
BIT
DESCRIPTION OF PARAMETER
With bit I, sets word length (See Table 8.10).
With bit 0, sets word length (See Table 8. 10).
Number of stop bits.
Set to 0 for I stop bit, or I for 2 stop bits.
With bit 4, sets parity selection (See Table 8.11).
With bit 3, sets parity selection (See Table 8.11).
With bits 6 and 7, sets baud rate (See Table 8.12).
With bits 5 and 7, sets baud rate (See Table 8.12).
With bits 5 and 6, sets baud rate (See Table 8.13).
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