_bios_serialcom

Syntax

#include <bios.h> unsigned _bios_serialcom(unsigned cmd, unsingned serialport, unsigned data);

Description

The _bios_serialcom routine uses INT 0x14 to provide serial communications services. The serialport argument is set to 0 for COM1, to 1 for COM2, and so on. The cmd argument can be set to one of the following manifest constants:

_COM_INIT

Initialize com port (data is the settings)

_COM_RECEIVE

Read a byte from port

_COM_SEND

Write a byte to port

_COM_STATUS

Get the port status

The data argument is ignored if cmd is set to _COM_RECEIVE or _COM_STATUS. The data argument for _COM_INIT is created by combining one or more of the following constants (with the OR operator):

_COM_CHR7 7 bits/character _COM_CHR8 8 bits/character _COM_STOP1 1 stop bit _COM_STOP2 2 stop bits _COM_NOPARITY no parity _COM_EVENPARITY even parity _COM_ODDPARITY odd parity _COM_110 110 baud _COM_150 150 baud _COM_300 300 baud _COM_600 600 baud _COM_1200 1200 baud _COM_2400 2400 baud _COM_4800 4800 baud _COM_9600 9600 baud

The default value of data is 1 stop bit, no parity, and 110 baud.

Return Value

The function returns a 16-bit integer whose high-order byte contains status bits. The meaning of the low-order byte varies, depending on the cmd value. The high-order bits are as follows:

Bit Meaning if Set 15 Timed out 14 Transmission-shift register empty 13 Transmission-hold register empty 12 Break detected 11 Framing error 10 Parity error 9 Overrun error 8 Data ready

When service is _COM_SEND, bit 15 is set if data cannot be sent.

When service is _COM_RECEIVE, the byte read is returned in the low-order bits if the call is successful. If an error occurs, any of the bits 9, 10, 11, or 15 is set.

When service is _COM_INIT or _COM_STATUS, the low-order bits are defined as follows:

Bit Meaning if Set 7 Receive-line signal detected 6 Ring indicator 5 Data-set-ready 4 Clear-to-send 3 Change in receive-line signal detected 2 Trailing-edge ring indicator 1 Change in data-set-ready status 0 Change in clear-to-send status

Portability

ANSI/ISO C	No
POSIX	No

Example

/* 9600 baud, no parity, one stop, 8 bits */ _bios_serialcom(_COM_INIT, 0, _COM_9600|_COM_NOPARITY|_COM_STOP1|_COM_CHR8); for(i=0; buf[i]; i++) _bios_serialcom(_COM_SEND, 0, buf[i]);