Click above to get retro games delivered to your door ever month!

_bios_serialcom
   Note-This function is not available when using OS/2.

Usage

   #include <bios.h>
   int _bios_serialcom(unsigned service, unsigned port,

                        unsigned data);

Description

   This function uses the BIOS to provide a number of serial RS232
   operations. The IBM BIOS only allows polled operation of the serial
   ports, not interrupt operation. The port argument is the number of the
   serial port to address. This is set to 0 for COM1 and 1 for COM2.

   There are four services provided:

   0 (inititialize) Set up the serial port as specified in the data
                    argument (see below).

   1 (send)         Transmit the data character through the selected serial
                    port

   2 (receive)      Accepts an input character through the selected serial
                    port.


   3 (status)       Return the current status of the selected serial port.

   The data argument for the initialize service is created by oring together
   one value from each of the following categories.

   Baud Rate

       Rate    Value
       -----   -----
       110        0
       150       32
       300       64
       600       96
       1200     128
       2400     160
       4800     192
       9600     224

   Data Word Length


       Word Length     Value
       -----------     -----
       7 data bits       2
       8 data bits       3

   Stop Bits

       No of bits  Value
       ----------  -----
          1          0
          2          4

   Parity

       Parity  Value
       ------  -----
       none      0
       odd       8
       even     24


Example 

   #include <stdio.h>
   #include <bios.h>
   #include <stdlib.h>

   int main()
   {
       unsigned com1_status;

       com1_status = _bios_serialcom(3,0,0);
       printf("COM1 status: %x\n",com1_status);
       return EXIT_SUCCESS;
   }

Return Value

   A 16 bit integer whose high byte contains status bits. The low byte will
   vary according to the service requested.


   The high byte status bits are as follows:

       Bit     Meaning when set
       ---     ----------------------------------
       15      Timed out
       14      Transmitter Shift register empty
       13      Transmitter Holding register empty
       12      Break detected
       11      Framing Error
       10      Parity Error
        9      Overrun Error
        8      Data Ready

   If the service requested is send, then bit 15 will be set if data could
   not be sent.

   If the service requested is recieve, then the byte read will be returned
   in the low byte, If an error occurred at least one bit in the high byte
   will be set, to indicate the source of the error.


   If the service requested is either initialize or status, additional
   status information will be returned in the low byte:

       Bit     Meaning when set
       ---     -------------------------------
        7      Data Carrier Detect (DCD) state
        6      Ring Indicator (RI) state
        5      Data Set Ready (DSR) state
        4      Clear To Send (CTS) state
        3      Change in DCD
        2      Change in RI
        1      Change in DSR
        0      Change in CTS

See Also

   BIOS package