Intel 80C186EA User Manual page 261

TIMER/COUNTER UNIT
sti
pop si
pop dx
pop ax
pop bp
ret
_set_time endp
timer_2_interrupt_routine proc far
push ax
push dx
cmp _msec, 99
jae bump_second
inc _msec
jmp short reset_int_ctl
bump_second:
mov _msec, 0
cmp _minute, 59
jae bump_minute
inc _second
jmp short reset_int_ctl
bump_minute:
mov _second, 0
cmp _minute, 59
jae bump_hour
inc _minute
jmp short reset_int_ctl
bump_hour:
mov _minute, 0
cmp _hour, 12
jae reset_hour
inc _hour
jmp reset_int_ctl
reset_hour:
mov _hour, 1
reset_int_ctl:
mov dx, EOI
mov ax, 8000h
out dx, al
pop dx
pop ax
iret
timer_2_interrupt_routine endp
lib_80186 ends
end
Example 9-1. Configuring a Real-Time Clock (Continued)
9-20
;enable interrupts
;restore saved registers
;restore caller's bp
;save registers used
;has 1 sec passed?
;if above or equal...
;reset millisecond
;has 1 minute passed?
;reset second
;has 1 hour passed?
;reset minute
;have 12 hours passed?
;reset hour
;non-specific end of interrupt