;The routine would be probably be framed by something like:

    LDA #XXX		      ; Position between 0-159
    LDX #$0X		      ; Offset for RESP0,X
    JSR TheMagicRoutine ; :-)
    STY HMP0,X		      ; Fine positioning value
    STA WSYNC
    STA HMOVE

;-----------------------------------------

TheMagicRoutine:
LD7E0: CMP    #$11    ;2
       BCS    LD7EA   ;2
       SBC    #$04    ;2
       BCS    LD7EA   ;2
       ADC    #$A5    ;2
LD7EA: STA    WSYNC   ;3
       STA    HMOVE   ;3

LD7EE: SBC    #$0F    ;2 
       BCS    LD7EE   ;2 ->5 cycles per iteration!

       EOR    #$07    ;2
       ASL            ;2
       ASL            ;2
       ASL            ;2
       ASL            ;2
       TAY            ;2
       STA    RESP0,X ;4
       STA    WSYNC   ;3
       STA    HMOVE   ;3
       RTS            ;6