Drawing the screen: SetPatternBuffer

       Name: SetPatternBuffer                                        [Show more]
       Type: Subroutine
   Category: Drawing the screen
    Summary: Set the high byte of the pattern buffer address variables
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * TT128 calls SetPatternBuffer


 Arguments:

   X                    The bitplane whose pattern address we should use


.SetPatternBuffer

 LDA pattBufferHiAddr,X ; Set the high byte of pattBufferAddr(1 0) to the
 STA pattBufferAddr+1   ; correct address for the pattern buffer for bitplane X

 LSR A                  ; Set pattBufferHiDiv8 to the high byte of the pattern
 LSR A                  ; buffer address, divided by 8
 LSR A
 STA pattBufferHiDiv8

 RTS                    ; Return from the subroutine