Assembly Code with Interrupts

[jmarcrum]

I have to modify this assembly code in order to make it use interrupts. Right now, when I push button 1 on the microprocessor the count increments once (the LED's count in binary, using only 3 LED's and only counting to 7 in binary). The second button on the microprocessor, when pushed, resets the count. I have the addreses for both button in the code.

However, my trouble is modifying this code. I HAVE to use interrupts. I need a lot of help with this!! I don't even know where to start putting the code in for this!! The interrupts are supposed to be timer interrupts and when they happen, use a poll to count up or count down. I guess I'm supposed to have code in there that enables them??

Here's my working code right now with NO interrupts...



;This program is a binary debouncing counter. Each press of switch 1 will count forward in binary with the board LEDs. Once count 8 is reached, the counter will reset itself back to count/state 0. At any time, switch 2 can be pressed to fully reset the counter.

gaddr equ fe8H ; Port G address register
gddr equ fe9H ; Port G data direction register
gout equ febH ; Port G output register
eaddr equ fe0H ; Port E address register
eddr equ fe1H ; Port E data direction register
eout equ fe3H ; Port E output register
din equ fdeH ; Port D input register
fin equ fe6H ; Port D input register
reg equ ffdH ; Working register set
sphi equ ffeH ; Stack pointer high
splo equ fffH ; Stack pointer low

org 002H ; Initializing the reset vector
start:
dw 0038H ; Restart at this address
org 038H ; Start in first available memory location

ldx reg, #00H ; Select working register set
ldx splo, #20H ; Set low byte of stack pointer
ldx sphi, #02H ; Set high byte of stack pointer
reset:
ldx r4, #00H ; Set register to state counter of 0

call initLED ; Access both DDRs and make all bits outputs
call allOff ; Turn off all LEDs
endless:
call delay ; Delay for debouncing the switch

SW1:
ldx r1, din ; Load r1 with SW1's value
and r1, #08H ; See if the switch was pressed
jp ne, SW2 ; If switch was not pressed do not increment the state
inc r4 ; Increment state if pressed

N1:
cp r4, #1 ; Switch (r4) ?= 1
jp ne, N2 ; If not equal, check next number
call allOff ; Turn off all LEDs
call oneOn ; LED: 001
call latchClk ; Latch clock for LED
jp caseOut ; break
N2:
cp r4, #2 ; Switch (r4) ?= 2
jp ne, N3 ; If not equal, check next number
call allOff ; Turn off all LEDs
call twoOn ; LED: 010
call latchClk ; Latch clock for LED
jp caseOut ; break
N3:
cp r4, #3 ; Switch (r4) ?= 3
jp ne, N4 ; If not equal, check next number
call allOff ; Turn off all LEDs
call threeOn ; LED: 011
call latchClk ; Latch clock for LED
jp caseOut ; break
N4:
cp r4, #4 ; Switch (r4) ?= 4
jp ne, N5 ; If not equal, check next number
call allOff ; Turn off all LEDs
call fourOn ; LED: 100
call latchClk ; Latch clock for LED
jp caseOut ; break
N5:
cp r4, #5 ; Switch (r4) ?= 5
jp ne, N6 ; If not equal, check next number
call allOff ; Turn off all LEDs
call fiveOn ; LED: 101
call latchClk ; Latch clock for LED
jp caseOut ; break
N6:
cp r4, #6 ; Switch (r4) ?= 6
jp ne, N7 ; If not equal, check next number
call allOff ; Turn off all LEDs
call sixOn ; LED: 110
call latchClk ; Latch clock for LED
jp caseOut ; break
N7:
cp r4, #7 ; Switch (r0r4) ?= 7
jp ne, N8 ; If not equal, check next number
call allOff ; Turn off all LEDs
call sevenOn ; LED: 111
call latchClk ; Latch clock for LED
jp caseOut ; break
N8:
cp r4, #8 ; Switch (r4) ?= 8
jp eq, reset ; If 8, reset

caseOut: ; End of case

SW2:
ldx r1, fin ; See what Switch 2 is doing
and r1, #40H ; See if the switch was pressed
jp nz, waitLoop; If switch was not pressed do not reset
jp reset ; Reset if the switch was pressed

;-----------------------------

initLED:
ldx eaddr, #01H; select Port E DDR in address register
ldx eddr, #00H ; make all pins outputs
ldx gaddr, #01H; select port G DDR in address register
ldx gddr, #00H ; make all pins outputs
ret
waitLoop:
ldx r1, din ; Load r1 with SW1's value
and r1, #08H ; See if the switch was pressed
jp z, waitLoop; If switch is still pressed, loop again
jp endless
delay:
ld r2, #05H ; initialize r2 = 10
outer:
clr r0 ; set r0 = 0000H for maximum possible delay
clr r1 ; set r1 = 0000H for maximum possible delay
inner:
decw rr0 ; decrement rr0 (inner loop)
jp ugt, inner ; !=0, continue inner loop
dec r2 ; decrement r2 (outer loop)
jp ugt, outer ; !=0, continue outer loop
ret
oneOn:
ldx gout, #01H ; enable the topmost row
ldx eout, #1EH; enable the rightmost column
ret ; LED: 00001
twoOn:
ldx gout, #01H ; enable the topmost row
ldx eout, #1DH; enable the rightmost - 1 column
ret ; LED: 00010
threeOn:
ldx gout, #01H ; enable the topmost row
ldx eout, #1CH; enable the rightmost and rightmost -1 column
ret ; LED: 00011
fourOn:
ldx gout, #01H ; enable the topmost row
ldx eout, #1BH; enable the rightmost - 2 column
ret ; LED: 00100
fiveOn:
ldx gout, #01H ; enable the topmost row
ldx eout, #1AH; enable the rightmost- 2 and rightmost column
ret ; LED: 00101
sixOn:
ldx gout, #01H ; enable the topmost row
ldx eout, #19H ; enable the rightmost-2 and rightmost1column
ret ; LED: 00110
sevenOn:
ldx gout, #01H ; enable the topmost row
ldx eout, #18H ; enable the rightmost2,1,& rightmost column
ret ; LED: 00111
latchClk:
orx eout, #80H; drive D1's latches' clock high
andx eout, #7fH ; drive D1's latches' clock low
ret
allOff:
ldx gout, #00H ; disable all rows
ldx eout, #1fH ; disable all columns
orx eout, #e0H ; drive 3 Port E clocks high
andx eout, #1fH ; drive 3 Port E clocks low
orx gout, #80H ; drive 1 Port G clock high
andx gout, #7fH ; drive 1 Port G clock low
ret

[Banfa]

You have not even said which processor you are using. Processor architecture particularly with reference to interrupts differs wildly from processor to processor.

For example I am currently working on 2 difference microprocessors

A PIC18F2620 which has 2 interrupt vectors at 8H and 18H which all peripherals are routed through.

ECOG1K which has 40 odd interrupt vectors one for each peripheral plus several exception traps located in the address range 4H - 40H


Generally what happens on most microprocessors when an interrupt occurs is the current processor state is saved to the stack and then the processor jumps (vectors) to a fixed location in memory. This location normally contains either the address of the function to run to handle the interrupt or a branch instruction to the function to run to handle the interrupt. These are the interrupt vectors.

You will need to check your processors datasheet/manual and the manual of the assembler you are using. Between these 2 documents you will normally find all the information required to configure and handle your interrupts and if you are lucky some example code.

[sicarie]

Moving to Misc Discussions. (I missed the C/C++ in there, but please feel free to move it back if it was in there.)

[Banfa]

I think the C/C++ connection is that almost all embedded C/C++ programmers have to do a little assembly too for a few low level drivers/functions, like for instance interrupt handling.

[sicarie]

I think the C/C++ connection is that almost all embedded C/C++ programmers have to do a little assembly too for a few low level drivers/functions, like for instance interrupt handling.

I would agree with that (though I personally didn't remember enough to follow all of it, I could still get the gist ;), but anyone else looking for help or reference with Assembly (without knowledge of C/C++) would be more likely to start out in the Misc Forum. (Well, they'd probably be most likely to start on Google, but...)