TempAlert.asm

ORG 400h
interrupter EQU 0h           ;Interrupts every 10 milliseconds to check temperature
thermometer EQU 1h           ;Measures temperature
dmac EQU 6h                  ;DMA controller: activates the interrupter whenever necessary
video EQU 11h                ;Video peripheral; displays error message whenever necessary
membuffer EQU 0000BBBBh      ;Initial alarm message location
maxcount EQU 10              ;Sets milliseconds amount to check temperature (10 ms)
maxtemp EQU 40               ;Sets maximum possible value for temperature (40°C)
counter DL 0                 ;Milliseconds counter
temperature DB 25            ;Initializes temperature to a mild/warm value (25°C)
CODE
START interrupter            ;Starts all peripherals
START thermometer
START dmac
START video
SETIM interrupter            ;Enables interrupter and thermometer to interrupt
SETIM thermometer
CLRIM dmac                   ;Disables DMAC interruptions (will be allowed whenever necessary)
loop: JMP loop               ;Loops instruction while waiting for interrupts
HALT
driver 0h, 1500h             ;Initializes the driver of the 0h peripheral, located at 1500h in memory
INL interrupter, R0          ;Saves milliseconds to R0
MOVL R0, counter             ;Updates milliseconds counter
CMPL maxcount, R0            ;Verifies if 10 ms have passed
JZ check                     ;If so, the temperature is checked
JNN check                    ;(Does the same if more than 10 ms have passed)
JMP loop                     ;Else, keeps looping
driver 1h, 1700h
check: MOVL #0h, counter     ;Resets counter
INB thermometer, R0          ;Saves temperature to R0
MOVB R0, temperature         ;Updates temperature
CMPB maxtemp, R0             ;Verifies if temperature is above 40°C
JNN alert                    ;If so, starts the DMAC to send the alarm signal
JMP loop                     ;Else, keeps looping
driver 6h, 1900h
alert: SETIM dmac            ;Enables DMAC interruptions
CLRIM interrupter            ;Disables all other interruptions while executing
MOVL #0h, counter            ;Resets counter
JSR alarm                    ;Jumps to subroutine: transfers alarm message
CLRIM dmac                   ;Disables DMAC interrupt until further notice
SETIM interrupter            ;Re-enables interruptions
JMP loop                     ;Keeps looping
alarm: PUSH R0               ;Saves register values to stack
PUSH R1
PUSH R2
MOVL membuffer, R0           ;Saves memory buffer initial location to R0
MOVL #200h, R2               ;Initializes counter to maximum data transfers (512 in hex)
write: OUTL R0, video        ;Displays error message
ADDL #4h, R0                 ;Proceeds to next data location
SUBL #1h, R2                 ;Updates counter
JNZ write                    ;If data transferring isn't done yet, keeps looping
POP R2                       ;Restores register values
POP R1
POP R0
RTI                          ;Returns from subroutine
END                          ;Terminates program