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⌂ ∞ ▽ Elite on the 6502

Drawing circles: CIRCLE2_b1

[NES version, Bank 7]

       Name: CIRCLE2_b1                                              [Show more]
       Type: Subroutine
   Category: Drawing circles
    Summary: Call the CIRCLE2 routine in ROM bank 1
  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:
             * TT128 calls CIRCLE2_b1




.CIRCLE2_b1

 LDA currentBank        ; If ROM bank 1 is already paged into memory, jump to
 CMP #1                 ; bank6
 BEQ bank6

 PHA                    ; Otherwise store the current bank number on the stack

 LDA #1                 ; Page ROM bank 1 into memory at $8000
 JSR SetBank

 JSR CIRCLE2            ; Call CIRCLE2, 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

.bank6

 JMP CIRCLE2            ; Call CIRCLE2, which is already paged into memory, and
                        ; return from the subroutine using a tail call