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⌂ ∞ Elite on the BBC Micro and NES

Universe: DrawSystemImage_b3

[NES version, Bank 7]

       Name: DrawSystemImage_b3                                      [Show more]
       Type: Subroutine
   Category: Universe
    Summary: Call the DrawSystemImage routine in ROM bank 3
  Deep dive: Splitting NES Elite across multiple ROM banks

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * TT25 calls DrawSystemImage_b3




.DrawSystemImage_b3

 STA storeA             ; Store the value of A so we can retrieve it below

 LDA currentBank        ; If ROM bank 3 is already paged into memory, jump to
 CMP #3                 ; bank8
 BEQ bank8

 PHA                    ; Otherwise store the current bank number on the stack

 LDA #3                 ; Page ROM bank 3 into memory at $8000
 JSR SetBank

 LDA storeA             ; Restore the value of A that we stored above

 JSR DrawSystemImage    ; Call DrawSystemImage, now that it is paged into memory

 JMP ResetBank          ; Fetch the previous ROM bank number from the stack and
                        ; page that bank back into memory at $8000, returning
                        ; from the subroutine using a tail call

.bank8

 LDA storeA             ; Restore the value of A that we stored above

 JMP DrawSystemImage    ; Call DrawSystemImage, which is already paged into
                        ; memory, and return from the subroutine using a tail
                        ; call