high speed hplot from assembly

*******************************
*
* HPLOT XLOC,YLOC FROM ASSEMBLY
*
* INPUT : XLOC  X COORD
*         YLOC  Y COORD
*
* OUTPUT: OR'D WITH SCREEN
*
*****************************


XBIT     DFB   #00
XBYTE    DFB   #00


MASKTEMP DFB   #00
                          ;-----------------------------



HPLOT    
         LDY   YLOC
         LDA   TLO,Y
         STA   SLO
         LDA   THI,Y
         STA   SHI


         LDA   XLOC
         LDY   #00
         CLC
DLOOPSV  CMP   #7         ;DIVIDE X COORDINATE BY 7
         BCC   DDONESV
         SEC
         SBC   #7
         INY
         CLC
         JMP   DLOOPSV


DDONESV


         TAX              ;Division done, now get the proper bit value
         LDA   MASK,X
         ORA   (SHI),Y    ;
         STA   (SHI),Y    ;PUT ON SCREEN


    
         RTS

MASK     DFB   #$01,#$02,#$04,#$08,#$10,#$20,#$40,#$80