ExEsonero.asm

;Exercise from: http://i46.tinypic.com/2whm49u.jpg

org 400h
disp equ 0h           ;Interrupts every 30 seconds and interruption programs DMAC
dmac equ 1h           ;DMAC, acquires 512B from an external drive and stores them in #buffer
car equ 2h            ;DMAC's current address register
wc equ 3h             ;DMAC's word counter
buffer equ 0BCBCh     ;Memory buffer starting address
datac equ 0CCh        ;Binary number 11001100, if present less than 11 times in buffer disp is masked
code
jsr init
seti
main: jmp main        ;Loops until interrupt
halt
init: inl #30, disp   ;Sets counter to 30 seconds and starts disp
start disp
ret
driver 0, 700h        ;Display driver
push R0
movl #512, R0
outl R0, wc           ;Sets word counter to 512
movl #0BCBCh, R0
outl R0, car          ;Sets initial memory location to buffer
start dmac
pop R0
rti
driver 1, 900h        ;DMAC driver
push R0
push R1
push R2
push R3
movl #512, R0         ;Serves as word counter
movl #0BCBCh, R1      ;Serves as current address register
movb #0CCh, R2        ;Stores data to compare
xorl R3, R3           ;Serves as counter, stores how many times the word is found in memory
find: cmpb (R1)+, R2  ;Compares data contained in memory with data to find
jnz notfound
addl #1, R3           ;Adds to the counter when the data is found
notfound: subl #1, R0 ;Updates word counter
jz exit               ;Exits when counter hits zero
jmp find
exit: cmpl #10, R3
jz ok                 ;If data appears 10 times, deactivates disp
jnn skip              ;If data appears more than 10 times, deactivation is skipped
ok: clear disp
skip: pop R3          ;Returns from subroutine
pop R2
pop R1
pop R0
rti
end