Holtek HT-IDE, Руководство пользователя

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org 08h ;timer/event 0 interrupt subroutine
cpl pb ;(6) ;generate square wave
reti ;end timer0 ISR
org 0ch ;timer/event 1 interrupt subroutine
reti ;for safeguard
start: ;
clr intc ;initialize registers
clr tmr0c ;to guarantee performance
clr tmr0h ;(interrupts)
clr tmr0l ;
clr tmr1c ;
clr tmr1 ;
set pac ;(ports)
set pbc ;(input mode)
set pcc ;
set pdc ;
main:
set pac ;(1) ;set port A to input port
clr pbc ;set port B to output port
clr pb ;
keyloop: ;(2) ;
mov a,pa ;test any input
cpl acc ;
sz acc ;if any?
call whichkey ;yes. find out which key
jmp keyloop ;no. repeat from keyloop
whichkey proc ;(3) ;find out which key
mov temp,a ;hold Acc content
mov a,0 ;zero table index
mov tblp,a ;
clr c ;c=0 (check each bit(key) by carry flag)
keynext: ;
rrc temp ;shift right through carry flag
sz status.0 ;if carry? (some key was pressed)
jmp timerset ;yes. output sound
inc tblp ;(4) ;no. table index point to next
inc tblp ;(2 bytes/key)
jmp keynext ;check next bit (key)
timerset: ;set timer to generate sound
mov a,5 ;enable timer0
mov intc,a ;
mov a,80h ;set timer0 mode (internal clock)
mov tmr0c,a ;
tabrdl sound ;(5) ;load freq.
mov a,sound ;(low byte)
mov tmr0l,a ;
inc tblp ;
tabrdl sound ;(6) ;(high byte)
mov a,sound ;
Chapter 16 Interrupt and timer applications
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