+-----------------------------------------+
| |
| ************************************* |
| * The IBM-PC COMMUNICATIONS library * |
| ************************************* |
| |
+-----------------------------------------+
An interrupt driven serial I/O lobrary
for Stand-Alone 8086 applicatons
using MICRO-C.
Copyright 1990-2000 Dave Dunfield
All rights reserved.
DK86 COMMUNICATIONS LIBRARY Page: 1
1. IBM-PC COMMUNICATIONS Library
The MICRO-C WINDOWING LIBRARY is a set of functions which
implement serial I/O with an 8250 type UART device, such as is used
on most PC serial cards.
The routines support interrupt driven reception, and XON/XOFF
software flow control, as well as setting and monitoring the RS-232
control signals.
To install these function into the 8086 library, place the
COMM.ASM and COMM.H files in the library subdirectory (usually \MC\LIB86), and
issue the following commands:
slib i=tiny a=comm
slib i=small a=comm
1.1 Function Definitions
The following functions are available in the IBM-PC
communications library:
CCLOSE CCLOSE
PROTOTYPE:
Cclose()
ARGUMENTS:
None
RETURN VALUE:
None
DESCRIPTION:
This function closes the communications port previously opened
using "Copen". The system interrupt vectors and all other hooks to
the comm port are restored.
This function must be called before any program using "Copen"
terminates, otherwise the communications port will be left in an
indeterminate state. If this is not done, there will be a
possibility of system crash if an interrupt is received from the
port after the program has terminated.
EXAMPLES:
Cclose(); /* Close comm port */
exit(0); /* And terminate */
CGETC CGETC
PROTOTYPE:
int Cgetc()
ARGUMENTS:
None
RETURN VALUE:
Character read from the communications port
DESCRIPTION:
This function reads a single character from the communications
port previously opened with "Copen". If no character is available,
"Cgetc" will wait for one.
EXAMPLES:
/* Get a string from the comm port */
while((c = cgetc()) != '\r')
*ptr++ = c;
*ptr = 0;
COPEN COPEN
PROTOTYPE:
int Copen(int port, int speed, int mode, int modem)
ARGUMENTS:
port - Comm port to use (1, 2, 3 or 4)
speed - Baudrate divisor to set
mode - Communications parameters to set
modem - Modem control lines to set
RETURN VALUE:
0 - Successful open
!0 - Requested comm port is not available
DESCRIPTION:
The "Copen" function opens a serial communications port on the
IBM PC for access. An independant interrupt handler and I/O
drivers are installed, which allow high speed full duplex
operation of the serial port with optional XON/XOFF flow control
of both receive and transmit streams.
Only one serial port may be accessed at a time using these
functions, If "Copen" is called more than once, it will
automatically close the last port before opening the new one.
The meaning of the "speed", "mode", and "modem" parameters if
documented in the "comm.h" header file.
An external "char" variable "Cflags" may be accessed to enable
or disable transparency of the serial channel. When "transparent"
is selected, XON/XOFF flow control is disabled, and all data is
sent and received with no changes. When operating in this mode,
you must insure that "Cgetc" is called frequently enough that the
256 byte internal receive buffer will not overflow.
Since "Cflags" is used by the interrupt handler, you should
disable and enable interrupts around any accesses to it.
EXAMPLES:
#include comm.h /* Get comm port defintions */
extern char Cflags;
/*
* Program to read & echo characters on the serial port
* in transparent mode. (Until ESCAPE char is received)
*/
main()
{
char c;
if(Copen(1, _2400, PAR_NO|DATA_8|STOP_1, SET_RTS|SET_DTR))
abort("Cannot access COM1");
disable(); /* Disable interrupts */
Cflags |= TRANSPARENT; /* Set transparency */
enable(); /* Re-enable interrupts */
while((c = Cgetc()) != 0x1B) /* Do until ESCAPE */
Cputc(c);
Cclose(); /* Close the serial port */
}
CPUTC CPUTC
PROTOTYPE:
Cputc(char c)
ARGUMENTS:
c - Character to write to communciation port
RETURN VALUE:
None
DESCRIPTION:
The "Cputc" function writes the given character to the
communcinations port previously opened by "Copen".
EXAMPLES:
while(*ptr) /* Write a string to comm port */
Cputc(*ptr++);
CSIGNALS CSIGNALS
PROTOTYPE:
int Csignals()
ARGUMENTS:
None
RETURN VALUE:
The modem input signals read from the open comm port
DESCRIPTION:
This function reads the modem input signals (DSR, CD, RI etc)
from the serial communication port previously opened by "Copen",
and returns them as an integer value.
The meaning of the individual bits in the value returned by
"Csignals" is documented in the "comm.h" header file.
EXAMPLES:
if(!(Csignals() & DSR)) {
Cclose();
abort("Modem not ready"); }
CTESTC CTESTC
PROTOTYPE:
int Ctestc()
ARGUMENTS:
None
RETURN VALUE:
0-255 - Character read from comm port
-1 - No character available
DESCRIPTION:
This function tests for a character from the communications
port previously opened with "Copen", and returns that character if
one if found. If no character is available, "Ctestc" returns -1.
EXAMPLES:
if((c = Ctestc()) == -1) {
Cclose();
abort("No character available"); }
DK86 COMMUNICATIONS LIBRARY
TABLE OF CONTENTS
Page
1. IBM-PC COMMUNICATIONS Library 1
1.1 Function Definitions 1