Programming application example of single chip microcomputer driving 74HC164

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;An example of microcontroller driving 74LS164/74HC164
;74HC164 is a serial input and parallel output data shift module. Every time a clock
pulse is sent to its clock end (CK), its current data line (DT) state is shifted to the output end and output. The data of 164
is latched at the rising edge of the clock, and the output shifts from A to H in sequence
;In this example, the bit operation plug-in developed by our site is used to facilitate the IO bit line setting and clearing operations

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;The process of sending a byte of data to 164
;R0----data/instruction byte to be sent 
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SENDTO164:
        PUSH R0
        PUSH R1
        CLRBIT CK_164 ;set c LOC k line is low 
        NOP
        NOP
        CLRBIT DT_164 ;set data line is low 
        LD R1,#08H
  SENDA_164:
        RLC R0 ;right shift R0,bit0 into C
        SETBIT DT_164 ;set data line
        JR C,SENDB_164 ;if C=1,skip
        CLRBIT DT_164 ;clear data line
       
  SENDB_164:
        NOP
        NOP 
        SETBIT CK_164 ;send one clock pulse
        NOP
        NOP
        NOP
        CLRBIT CK_164 ;
        DEC R1
        JR NZ,SENDA_164 
        
SEND164_BACK:
        P OP R1
        POP R0
        RET 
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