Intel 80C188EC User Manual page 361

SERIAL COMMUNICATIONS UNIT
$mod186
name example_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 xxxxh
S1STS equ
S1CON equ
S1TBUF equ
;
lib_80186 segment public 'code'
assume cs:lib_80186
public _send_slave_cmd
_send_slave_cmd proc far
push bp
mov
; get slave command off the stack
_slave_cmd equ
push ax
push dx
mov
in
mov
mov
out
mov
mov
out
pop
pop
pop
ret
_send_slave_cmd endp
lib_80186 ends
end
Example 11-6. Master/Slave — The _send_slave_command Routine
11-32
xxxxh ; Serial Port 1 Status register
xxxxh ; Serial Port 1 Control register
xxxxh ; Serial Port 1 Transmit Buffer register
; save caller's bp
bp, sp ; get current top of stack
word ptr [bp+6]
; save registers that are modified
dx, S1STS ; clear any pending exceptions
ax, dx
dx, S1CON ; prepare to send command
ax, 0003h ; Mode 3
dx, ax
dx, S1TBUF ; select slave
ax, _slave_cmd ; get command to send to slave
dx, al ; send it
dx ; restore saved registers
ax
bx ; restore caller's bp