3-33
06 Close RS-485 multi-bus (release RS-485 bus)
Entry Parameters: AH = 6
Returned Values: None
void TC_485_close()
{
regs.h.ah = 6;
int86(0x33,&regs,&regs);
}
NOTE:
1) While the RS-485 post is used for serial input/output (character I/O)
communication. The application must enable RS-485 first to set
communication characteristic and make the system ready for serial I/O and
then open its RS-485 to occupy the bus prior to reading or writing data. The
application should close the RS-485 port when the data pack transmission
completed and release the bus to be used by other terminals. And the
application should disable the RS-485 port while all data packs are send or
received.
Ex. Enable RS-485 port for character based communication
?
Open RS-485 to occupy the bus
?
Repeat { read/write data to RS-485 port } until completed
?
Close RS-485 to release the bus
?
Disable RS-485 port for character based communication
2) When the RS-422/485 is controlled by use of INT 33H and the port is
assigned as host. The protocol must set as “NONE”.
3) If the RS-422/485 port acts as serial port, and the flow of hand shaking will
be controlled by user program instead of XON/XOFF. You must set the flow
control as “NONE”.