Tcl for Embedded Applications

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TinyTcl - BIOS Interface Commands

These are some ugly S.O.B.'s from the early days of the PC that are usually always present on any DOS or embedded DOS system that has PC-like hardware, even if it's a ruggedized handheld, or whatever.

bios_memsize - returns the memory size according to the BIOS.

This value does not change as memory is being allocated and freed. (Use memfree and stackfree for that.)

bios_memsize usually returns in the vicinity of 550,000 bytes on a PC compatible with 640K directly addressable, depending on the drivers loaded, etc. On Windows, it returns a much lower number but Windows can dynamically grow the memory a DOS window is using. On Windows you can also mess with the MS-DOS prompt properties, leave it on auto or set it to an explicit size, which should affect what bios_memsize reports.

bios_equiplist - return the equipment list according to the BIOS

This is a very primitive command, probably dating back to the original PC. You can't find out much, and it's all packed into the word that's returned. If you really need this data, this code should be expanded to unpack it for you. We have not included documentation on what the bits mean... sorry.

com - interface to BIOS serial communications

Port 0 is COM1, port 1 is COM2, etc.

• com init port [data]
  • If data is not specified, initializes port to 9600 baud, no parity, 8 data bits and one stop bit. If data is specified, it is a logical OR of a set of bit patterns, defined by ORing from the values below:

#define _COM_CHR7       0x02    /* 7 data bits */
#define _COM_CHR8       0x03    /* 8 data bits */
#define _COM_STOP1      0x00    /* 1 stop bit */
#define _COM_STOP2      0x04    /* 2 stop bits */
#define _COM_NOPARITY   0x00    /* no parity */
#define _COM_EVENPARITY 0x18    /* even parity */
#define _COM_ODDPARITY  0x08    /* odd parity */
#define _COM_110        0x00    /* 110 baud */
#define _COM_150        0x20    /* 150 baud */
#define _COM_300        0x40    /* 300 baud */
#define _COM_600        0x60    /* 600 baud */
#define _COM_1200       0x80    /* 1200 baud */
#define _COM_2400       0xa0    /* 2400 baud */
#define _COM_4800       0xc0    /* 4800 baud */
#define _COM_9600       0xe0    /* 9600 baud */

• com send port data - Emits data to the specified port.

• com receive port - Returns zero or more bytes read so far from the specified port.

• com status port - Returns the status of the port.

See also DOS commands and DOS video commands.