Skip to navigation

⌂ ∞ ▽ Elite on the 6502

Start and end: Interrupts_b1

[NES version, Bank 1]

       Name: Interrupts_b1                                           [Show more]
       Type: Subroutine
   Category: Start and end
    Summary: The IRQ and NMI handler while the MMC1 mapper reset routine is
             still running

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * Vectors_b1 calls Interrupts_b1




.Interrupts_b1

IF _NTSC

 RTI                    ; Return from the IRQ interrupt without doing anything
                        ;
                        ; This ensures that while the system is starting up and
                        ; the ROM banks are in an unknown configuration, any IRQ
                        ; interrupts that go via the vector at $FFFE and any NMI
                        ; interrupts that go via the vector at $FFFA will end up
                        ; here and be dealt with
                        ;
                        ; Once bank 7 is switched into $C000 by the ResetMMC1
                        ; routine, the vector is overwritten with the last two
                        ; bytes of bank 7, which point to the IRQ routine

ENDIF