Utility routines: ZES1

       Name: ZES1                                                    [Show more]
       Type: Subroutine
   Category: Utility routines
    Summary: Zero-fill the page whose number is in X
    Context: See this subroutine in context in the source code
 Variations: See code variations for this subroutine in the different versions
 References: This subroutine is called as follows:
             * LYN calls ZES1
             * ZERO calls ZES1


 Arguments:

   X                    The page we want to zero-fill


.ZES1

 LDY #0                 \ If we set Y = SC = 0 and fall through into ZES2
 STY SC                 \ below, then we will zero-fill 255 bytes starting from
                        \ SC - in other words, we will zero-fill the whole of
                        \ page X

 STX SC+1               \ We want to zero-fill page X, so store this in the
                        \ high byte of SC, so SC(1 0) is now pointing to page X