3-26
Returned Values: AL = 0 ;port is available
1 ;port is busy
int TC_ready(int wait)
{
int i;
do {
regs.h.ah=0x61;
int86(0x21,&regs,&regs);
} while (wait && regs.h.al);
return(regs.h.al);
}
3.4. Serial I/O for RS-232 and RS-485
The system allow to the RS-232 and RS-485 to serve serial input/output
(character mode I/O) no matter the port is assigned as host or serial port.
However, if the port is assigned as host, must select “NONE” as its active
protocol.
The INT 34H is dedicated for RS-232 and INT33H is dedicated for RS-485
and the both function calls are functional for host and serial port.
RS-232 port serial I/O using INT 34H
01 Input data
Entry Parameters: AH = 1
Returned Values: 1) if a character received
AH = 0
AL = Data character
2) if no character received
AH = 1
AL = undefined
unsigned char TC_232_char_I()
{
regs.h.ah = 1;
int86(0x34,&regs,&regs);
if (regs.h.ah == 0)
return(regs.h.al);
return(255);
}