80C186EB/80C188EB Microprocessor User's Manual - CEUNES

SERIAL COMMUNICATIONS UNIT$mod186nameexample_master_send_slave_command;************************************************************************;; send_slave_cmd; FUNCTION: This function transmits a slave command, _slave_cmd, over; the serial network to a previously addressed slave.; SYNTAX: extern void far send_slave_cmd (int slave_cmd);; INPUTS: _slave_cmd (command to send to addressed slave);; OUTPUTS: None;; NOTE: Parameters are passed on the stack as required by; high-level languages. Example assumes PCB is in I/O space.;************************************************************************;; substitute register offsets in place of xxxxhS1STS equ xxxxh ; Serial Port 1 Status registerS1CON equ xxxxh ; Serial Port 1 Control registerS1TBUF equ xxxxh ; Serial Port 1 Transmit Buffer register;lib_80186segment public ‘code’assume cs:lib_80186public_send_slave_cmd_send_slave_cmd proc farpush bp ; save caller’s bpmov bp, sp ; get current top of stack; get slave command off the stack_slave_cmd equ word ptr [bp+6]push ax ; save registers that are modifiedpush dx_send_slave_cmdendpmov dx, S1STS ; clear any pending exceptionsin ax, dxmov dx, S1CON ; prepare to send commandmov ax, 0003h ; Mode 3out dx, axmov dx, S1TBUF ; select slavemov ax, _slave_cmd ; get command to send to slaveout dx, al ; send itpop dx ; restore saved registerspop axpop bx ; restore caller’s bpretlib_80186endsendExample 10-6. Master/Slave — The _send_slave_command Routine10-35