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}
19 Set COM1 port as RS485 or modem
This function call is used to set COM1 port as RS485 serial port or modem
when you have the internal modem interface installed. Before you can start
to use modem for communication, you must set COM1 port as modem.
Entry Parameters: AH = 19
AL = 0 ; set as RS485
1 ; set as modem
Returned Value: None
void TC_modem_port(int status)
{
regs.h.ah= 0x19;
regs.h.al= status;
int86(0x21,®s,®s);
}
3.3. Host Port for Multi-point Protocol I/O (INT21H)
1C Setup multi-point address
Entry Parameters: AH = 0x1C
BH = 06
AL = 'A'..'Y','0'..'6'
Returned Values: None
void TC_set_address(char status)
{
regs.h.ah= 0x1C;
regs.h.al= status;
regs.h.bh= 6;
int86(0x21,®s,®s);
}
1C Set polling timeout duration
Entry Parameters: AH = 0x1C
BH = 09
AL = 0-255 ;timeout period with base
timeout cycle 80ms
Returned Values: None ;timeout period is 160ms
when set AL=2; AL=0 for no
timeout
void TC_time_out(int status)