ExEsame9.asm

;Exercise on slide 9: July 13th, 2000 exam

org 400h
timer1 equ 0h
timer2 equ 1h
synch equ 0AAAAh         ;Initialized to 0, put to 1 when synching (when interrupt1 reaches), checked if 1 when synched (when interrupt2 reaches)
                         ;Is put to 0 in that case, else CPU imports a longword from timer2 set at buffer and system is reset
time1 equ 0BBBBh         ;Time in between interruptions (timer1 interrupts)
time2 equ 0CCCCh         ;Time in between interruptions (timer2 interrupts)
buffer equ 0DDDDh        ;Memory buffer
code
jsr init                 ;Initializes devices
main: jmp main           ;Stalls until interrupt is received
halt
init: movb #0, synch     ;Initializes synch to 0, then starts devices
outb time1, timer1       ;Initializes timers to respective time counters
outb time2, timer2
start timer1
start timer2
seti
setim timer1
setim timer2
ret
driver 0, 700h           ;Driver for timer1
clrim timer2
movb #1, synch           ;Sets synch byte to 1 and returns to main
start timer1
rti
driver 1, 1100h          ;Driver for timer2
push R0
clrim timer1             ;Disables timer1 interrupts for driver execution
movb #1, R0
cmpb synch, R0           ;Checks if current synch value is 1
jz unsynch               ;If so, resets it to 0
inl timer2, buffer       ;If not, imports longword from timer
jsr init                 ;Restarts devices
unsynch: movb #0, synch  ;Unsynchs devices
start timer2
resume: setim timer1     ;Returns from driver
pop R0
rti
end