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⌂ ∞ ▽ Elite on the BBC Micro and NES

Combat demo: ShowScrollText_b6

[NES version, Bank 7]

       Name: ShowScrollText_b6                                       [Show more]
       Type: Subroutine
   Category: Combat demo
    Summary: Call the ShowScrollText routine in ROM bank 6
  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:
             * DEATH2 calls ShowScrollText_b6
             * Main flight loop (Part 15 of 16) calls ShowScrollText_b6




.ShowScrollText_b6

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

 LDA currentBank        ; If ROM bank 6 is already paged into memory, jump to
 CMP #6                 ; bank13
 BEQ bank13

 PHA                    ; Otherwise store the current bank number on the stack

 LDA #6                 ; Page ROM bank 6 into memory at $8000
 JSR SetBank

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

 JSR ShowScrollText     ; Call ShowScrollText, 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

.bank13

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

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