diff options
Diffstat (limited to 'basics/persist.s')
| -rw-r--r-- | basics/persist.s | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/basics/persist.s b/basics/persist.s index 430654f..3e7c439 100644 --- a/basics/persist.s +++ b/basics/persist.s @@ -11,10 +11,9 @@ ;; Last but not least, all of this is done thanks to the MMC1 chip. Thus, this ;; file is also a minimalistic example on how to configure it, even if it ;; doesn't take full advantage of it (e.g. we are not doing any bank switching). -;; Because of this, note that we are not using a proper linker configuration for -;; it (I'm using cc65's default, which is tailored for NROM chips). Thus, bank -;; switching will actually never work under this setup. Bank switching is -;; covered through other examples like `basics/unrom.s`. +;; A base configuration for this chip can be found in `config/mmc1.cfg`. For +;; better grasping bank switching though refer to other examples like +;; `basics/unrom.s`. .segment "HEADER" .byte 'N', 'E', 'S', $1A @@ -36,9 +35,12 @@ .addr reset .addr irq -.segment "STARTUP" -.segment "CODE" +;; Unused. This is the swappable PRG-ROM bank as per `config/mmc1.cfg`. +.segment "BANK0" +.byte $00 +;; This is the fixed PRG-ROM bank as per `config/mmc1.cfg`. +.segment "BANK1" ;; Unused nmi: @@ -65,7 +67,7 @@ reset: ;; point to any address range of $8000-$FFFF. If you want to be sure about ;; it, you can simply do: `lda #%10000000` and then `sta $8000`. This will ;; ensure that the chip is reset. That being said, a micro-optimization can - ;; be performed by taking advantage that the "CODE" segment resides above + ;; be performed by taking advantage that the "BANK1" segment resides above ;; address $8000. Then, you can use the `inc` instruction which first writes ;; the old value before the incremented one. All having thus the same effect ;; but saving 2 bytes. I know it's somewhat obfuscated and it's done for @@ -164,4 +166,10 @@ reset_mmc1: @loop: jmp @loop -.segment "CHARS" +;; Unused +.segment "CHR0" +.byte $00 + +;; Unused +.segment "CHR1" +.byte $00 |