Skip to navigation

⌂ ∞ Elite on the BBC Micro and NES

Moving: MVS5_b0

[NES version, Bank 7]

       Name: MVS5_b0                                                 [Show more]
       Type: Subroutine
   Category: Moving
    Summary: Call the MVS5 routine in ROM bank 0
  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:
             * HAS1 calls MVS5_b0




.MVS5_b0

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

 LDA currentBank        ; If ROM bank 0 is already paged into memory, jump to
 CMP #0                 ; bank21
 BEQ bank21

 PHA                    ; Otherwise store the current bank number on the stack

 LDA #0                 ; Page ROM bank 0 into memory at $8000
 JSR SetBank

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

 JSR MVS5               ; Call MVS5, 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

.bank21

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

 JMP MVS5               ; Call MVS5, which is already paged into memory, and
                        ; return from the subroutine using a tail call