键盘扫描汇编程序

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         acall delay20ms
         mov r0,#8
         ajmp scanend
row21:   cjne a,#0ddh,row22
         mov r0,#9
         acall delay20ms
         ajmp scanend       
row22:   cjne a,#0bdh,row23
         mov r0,#10
         acall delay20ms
         ajmp scanend
row23:   mov r0,#11
         acall delay20ms
         ajmp scanend

row3:   mov key,#0fbh
        mov a,key
        cjne a,#0fbh,row3scan
        ajmp row4
row3scan:cjne a,#0ebh,row31
         mov r0,#4
         acall delay20ms
         ajmp scanend
row31:   cjne a,#0dbh,row32
         mov r0,#5
         acall delay20ms
         ajmp scanend       
row32:   cjne a,#0bbh,row33
         mov r0,#6
         acall delay20ms
         ajmp scanend
row33:   mov r0,#7
         acall delay20ms
         ajmp scanend

row4:    mov key,#0f7h
         mov a,key
         cjne a,#0e7h,row41
         mov r0,#0
         acall delay20ms
         ajmp scanend
row41:   cjne a,#0d7h,row42
         mov r0,#1
         acall delay20ms
         ajmp scanend       
row42:   cjne a,#0b7h,row43
         mov r0,#2
         acall delay20ms
         ajmp scanend
row43:   mov r0,#3
         acall delay20ms
         ajmp scanend

scanend:ret

;判断是否松开
keyoff:  mov key,#0fh
         mov a,key
         cjne a,#0fh,keyret
         sjmp keyoff
keyret:  acall delay20ms
         ret
;!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
;!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
;12Mhz Crystal!!!!!!!!!!!!!!!!!!!!!!!12周期单片机
delay20ms:mov r7,#250
delay20msd0:mov r6,#60
delay20msd1:djnz r6,$
            djnz r7,delay20msd0
            ret
           
tab:db 11100111b,10000100b,11010011b,11010110b,10110100b,

01110110b,01110111b,11000100b,11110111b,11110110b

db 11110101b,00110111b,01100011b,10010111b,01110011b,

01110001b,01100111b,10110101b,00100001b,10000111b
db 00100011b,00010101b,00010111b,11110001b,11110100b,10110110b

         end

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，键盘扫描汇编程序