DATA_HI EQU 10H ; HI half of words
DATA_LO EQU 11H ; LO half of words
ROM_AD EQU 12H ; the address of 93c46

TEMR EQU 13H ;
BIT_COUNT EQU 14H
;
CM_EWEN EQU 30H
CM_EWDS EQU 0H
;RA
CS EQU 0
SK EQU 1
DI EQU 2

;---------------
;used transmiting the first bits in commands
START_BITS
?BCF RA,SK
?NOP
?BSF RA,CS
?NOP
?BSF RA,DI
?NOP
?BSF RA,SK
?NOP
?BCF RA,SK
?RETLW 0
;------------------
;the route of transmitting a byte
TRMIT?? ;
?MOVLW 8
?MOVWF BIT_COUNT
TRM0
?BCF 3,0
?BCF RA,SK
?RLF TEMR
?BTFSS 3,0
?GOTO ^+3
?BSF RA,DI
?GOTO ^+2
?BCF RA,DI
?NOP
?BSF RA,SK
?DECFSZ BIT_COUNT
?GOTO TRM0
?RETLW 0H
;---------------------
;the route of receiving a byte
RECEIVE
?MOVLW 8H
?MOVWF BIT_COUNT
?CLRF TEMR
RV0
?BSF RA,SK
?NOP
?NOP
?BSF 3,0
?BCF RA,SK
?NOP
?BTFSS RA,DO
?BCF 3,0
?RLF TEMR
?DECFSZ BIT_COUNT
?GOTO RV0
?RETLW 0H
;=============================
; read a word data.
; the data in ROM_AD is the address of
; the word, which come from main route
RD_ROM
?MOVLW 080H
?IORWF ROM_AD
?MOVFW ROM_AD
?MOVWF TEMR

?CALL START_BITS
?CALL TRMIT
RC_DA
?NOP
?BCF RA,SK
?NOP
?BTFSC RA,DO
?RETLW 0FFH
?CALL RECEIVE
?MOVFW TEMR
?MOVWF DATA_HI

?CALL RECEIVE
?MOVFW TEMR
?MOVWF DATA_LO
?BCF RA,CS
?RETLW 0
;=============================
; write a word data.
; the data in ROM_AD is the address of
; the word, which come from main route
WRT
?MOVLW 40H
?IORWF ROM_AD
?MOVFW ROM_AD
?MOVWF TEMR

?CALL START_BITS
?CALL TRMIT

?MOVFW DATA_HI
?MOVWF TEMR
?CALL TRMIT
?MOVFW DATA_LO
?MOVWF TEMR
?BCF RA,CS
?RETLW 0H

;-----------------------------
EWEN
?MOVLW CM_EWEN
?GOTO EWDS+1
EWDS
?MOVLW CM_EWDS
?MOVWF ROM_AD
?MOVFW ROM_AD
?MOVWF TEMR

?CALL START_BITS
?CALL TRMIT
?BCF RA,CS
?RETLW 0H