timer2.htm

这是8位微处理器的Verilog源代码

        ldi     acc,#F0h
        stacc   port            ; port gets 0xFF

        ldi     acc,#00h        ; low byte is in mem loc 0
        stm     acc,#0h

loop:   call    delay1_sec

        ldm     acc,#0h         ; get counter value
        oracci  #F0h            ; initially, both LE_L are high
        andacci #dfh            ; set lsb LDE LE_L low
        stacc   port            ; write to port
        oracci  #20h            ; set it back high
        stacc   port            ; and write to port

disp_high_byte:
        ldm     acc,#0h         ; get the data
        shracc
        shracc
        shracc
        shracc                  ; get the high nibble
        oracci  #F0h            ; initially, both LE_L are high
        andacci #efh            ; set msb LE_H low
        stacc   port            ; write to port
        oracci  #10h            ; set LE_L back high (latch data into LED)
        stacc   port            ; and write to port

        ldm     acc,#0h         ; get counter from mem
        addacci #1h             ; increment it and
        stm     acc,#0h         ; save to mem

        jmp     loop



delay1_sec:
        push    acc
        ldi     acc,#ffh
yy:     call    delay1_ms
        subacci #01h
        cmpacci #00h
        jne     yy
        pop     acc
        ret

delay1_ms:
        push    acc
        ldi     acc,#ffh
xx:     subacci #01h
        cmpacci #00h
        cmpacci #00h
        cmpacci #00h
        jne     xx
        pop     acc
        ret

        END