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⌂ ∞ Elite on the BBC Micro and NES

Drawing the screen: GetNameAddress

[NES version, Bank 3]

       Name: GetNameAddress                                          [Show more]
       Type: Subroutine
   Category: Drawing the screen
    Summary: Get the addresses in the nametable buffers for a given tile

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * DrawImageFrame calls GetNameAddress
             * DrawSmallBox calls GetNameAddress




 Arguments:

   XC                   The tile column

   YC                   The tile row



 Returns:

   SC(1 0)              The address in nametable buffer 0 for the tile

   SC2(1 0)             The address in nametable buffer 1 for the tile



.GetNameAddress

 JSR GetRowNameAddress  ; Get the addresses in the nametable buffers for the
                        ; start of character row YC, as follows:
                        ;
                        ;   SC(1 0) = the address in nametable buffer 0
                        ;
                        ;   SC2(1 0) = the address in nametable buffer 1

 LDA SC                 ; Set SC(1 0) = SC(1 0) + XC
 CLC                    ;
 ADC XC                 ; Starting with the low bytes
 STA SC                 ;
                        ; So SC(1 0) contains the address in nametable buffer 0
                        ; of the text character at column XC on row YC

 STA SC2                ; Set SC2(1 0) = SC2(1 0) + XC
                        ;
                        ; Starting with the low bytes
                        ;
                        ; So SC2(1 0) contains the address in nametable buffer 1
                        ; of the text character at column XC on row YC

 BCC nadd1              ; If the above addition overflowed, then increment the
 INC SC+1               ; high bytes of SC(1 0) and SC2(1 0) accordingly
 INC SC2+1

.nadd1

 RTS                    ; Return from the subroutine