From b35032f28def8beb8583bf5424257500af3cbbc5 Mon Sep 17 00:00:00 2001 From: Greg Shuflin Date: Sun, 30 Jan 2022 11:46:51 -0800 Subject: [PATCH] Simple ROM with single-color screen --- README.md | 4 + common/InitSNES.asm | 263 +++++++++++++++++++++++++++++++++++++ justfile | 6 + simple-rom/header.inc | 61 +++++++++ simple-rom/simple_rom.asm | 28 ++++ simple-rom/simple_rom.link | 2 + 6 files changed, 364 insertions(+) create mode 100644 common/InitSNES.asm create mode 100644 simple-rom/header.inc create mode 100644 simple-rom/simple_rom.asm create mode 100644 simple-rom/simple_rom.link diff --git a/README.md b/README.md index b052056..6c5b8ed 100644 --- a/README.md +++ b/README.md @@ -4,6 +4,10 @@ This repo is a playground for messing around with SNES assembly. It uses the [wla-dx](https://github.com/vhelin/wla-dx) assembler toolchain. +## Roms + +* `simple-rom` - this is more or less following bazz's tutorial here: https://wiki.superfamicom.org/writing-your-first-snes-program + # Resources diff --git a/common/InitSNES.asm b/common/InitSNES.asm new file mode 100644 index 0000000..c7ca3c6 --- /dev/null +++ b/common/InitSNES.asm @@ -0,0 +1,263 @@ +;------------------------------------------------------------------------ +;- Written by: Neviksti +;- If you use my code, please share your creations with me +;- as I am always curious :) +;------------------------------------------------------------------------ + + +;---------------------------------------------------------------------------- +; InitSNES -- my "standard" initialization of SNES memory and registers +;---------------------------------------------------------------------------- +.MACRO InitSNES + sei ;disable interrupts + clc ;switch to native mode + xce + + REP #$38 ; mem/A = 16 bit, X/Y = 16 bit + ;decimal mode off + + LDX #$1FFF ;Setup the stack + TXS ;Transfer Index X to Stack Pointer Register + + ;do the rest of the initialization in a routine + JSL $008000 + + SEP #$20 ; mem/A = 8 bit +.ENDM + +;---------------------------------------------------------------------------- + +.BANK 0 SLOT 0 +.ORG 0 +.SECTION "InitializeSNESCode" FORCE + +InitializeSNES: + PHK ;set Data Bank = Program Bank + PLB + + LDA #$0000 ;set Direct Page = $0000 + TCD ;Transfer Accumulator to Direct Register + + LDX $1FFD ;we clear all the mem at one point ... + STX $4372 ;so save the return address in a place that won't get overwritten + LDX $1FFF + STX $4374 + + SEP #$20 ; mem/A = 8 bit + REP #$10 + + LDA #$8F + STA $2100 ;turn screen off for now, set brightness to normal + + LDX #$2101 +_Loop00: ;regs $2101-$210C + STZ $00,X ;set Sprite,Character,Tile sizes to lowest, and set addresses to $0000 + INX + CPX #$210D + BNE _Loop00 + +_Loop01: ;regs $210D-$2114 + STZ $00,X ;Set all BG scroll values to $0000 + STZ $00,X + INX + CPX #$2115 + BNE _Loop01 + + LDA #$80 ;reg $2115 + STA $2115 ; Initialize VRAM transfer mode to word-access, increment by 1 + + STZ $2116 ;regs $2117-$2117 + STZ $2117 ;VRAM address = $0000 + + ;reg $2118-$2119 + ;VRAM write register... don't need to initialize + + STZ $211A ;clear Mode7 setting + + LDX #$211B +_Loop02: ;regs $211B-$2120 + STZ $00,X ;clear out the Mode7 matrix values + STZ $00,X + INX + CPX #$2121 + BNE _Loop02 + + ;reg $2121 - Color address, doesn't need initilaizing + ;reg $2122 - Color data, is initialized later + + LDX #$2123 +_Loop03: ;regs $2123-$2133 + STZ $00,X ;turn off windows, main screens, sub screens, color addition, + INX ;fixed color = $00, no super-impose (external synchronization), + CPX #$2134 ;no interlaced mode, normal resolution + BNE _Loop03 + + ;regs $2134-$2136 - multiplication result, no initialization needed + ;reg $2137 - software H/V latch, no initialization needed + ;reg $2138 - Sprite data read, no initialization needed + ;regs $2139-$213A - VRAM data read, no initialization needed + ;reg $213B - Color RAM data read, no initialization needed + ;regs $213C-$213D - H/V latched data read, no initialization needed + + STZ $213E ;reg $213E - might not be necesary, but selects PPU master/slave mode + ;reg $213F - PPU status flag, no initialization needed + + ;reg $2140-$2143 - APU communication regs, no initialization required + + ;reg $2180 - read/write WRAM register, no initialization required + ;reg $2181-$2183 - WRAM address, no initialization required + + ;reg $4016-$4017 - serial JoyPad read registers, no need to initialize + + + STZ $4200 ;reg $4200 - disable timers, NMI,and auto-joyread + + LDA #$FF + STA $4201 ;reg $4201 - programmable I/O write port, initalize to allow reading at in-port + + ;regs $4202-$4203 - multiplication registers, no initialization required + ;regs $4204-$4206 - division registers, no initialization required + + ;regs $4207-$4208 - Horizontal-IRQ timer setting, since we disabled this, it is OK to not init + ;regs $4209-$420A - Vertical-IRQ timer setting, since we disabled this, it is OK to not init + + STZ $420B ;reg $420B - turn off all general DMA channels + STZ $420C ;reg $420C - turn off all H-MA channels + + STZ $420D ;reg $420D - ROM access time to slow (2.68Mhz) + + LDA $4210 ;reg $4210 - NMI status, reading resets + + ;reg $4211 - IRQ status, no need to initialize + ;reg $4212 - H/V blank and JoyRead status, no need to initialize + ;reg $4213 - programmable I/O inport, no need to initialize + + ;reg $4214-$4215 - divide results, no need to initialize + ;reg $4216-$4217 - multiplication or remainder results, no need to initialize + + ;regs $4218-$421f - JoyPad read registers, no need to initialize + + ;regs $4300-$437F + ;no need to intialize because DMA was disabled above + ;also, we're not sure what all of the registers do, so it is better to leave them at + ;their reset state value + + JSR ClearVRAM ;Reset VRAM + JSR ClearPalette ;Reset colors + + ;**** clear Sprite tables ******** + + STZ $2102 ;sprites initialized to be off the screen, palette 0, character 0 + STZ $2103 + LDX #$0080 + LDA #$F0 +_Loop08: + STA $2104 ;set X = 240 + STA $2104 ;set Y = 240 + STZ $2104 ;set character = $00 + STZ $2104 ;set priority=0, no flips + DEX + BNE _Loop08 + + LDX #$0020 +_Loop09: + STZ $2104 ;set size bit=0, x MSB = 0 + DEX + BNE _Loop09 + + ;**** clear WRAM ******** + + STZ $2181 ;set WRAM address to $000000 + STZ $2182 + STZ $2183 + + LDX #$8008 + STX $4300 ;Set DMA mode to fixed source, BYTE to $2180 + LDX #wram_fill_byte + STX $4302 ;Set source offset + LDA #:wram_fill_byte + STA $4304 ;Set source bank + LDX #$0000 + STX $4305 ;Set transfer size to 64k bytes + LDA #$01 + STA $420B ;Initiate transfer + + LDA #$01 ;now set the next 64k bytes + STA $420B ;Initiate transfer + + PHK ;make sure Data Bank = Program Bank + PLB + + CLI ;enable interrupts again + + LDX $4372 ;get our return address... + STX $1FFD + LDA $4374 + STA $1FFF + RTL + +wram_fill_byte: +.db $00 + +;---------------------------------------------------------------------------- +; ClearVRAM -- Sets every byte of VRAM to zero +; In: None +; Out: None +; Modifies: flags +;---------------------------------------------------------------------------- +ClearVRAM: + pha + phx + php + + REP #$30 ; mem/A = 8 bit, X/Y = 16 bit + SEP #$20 + + LDA #$80 + STA $2115 ;Set VRAM port to word access + LDX #$1809 + STX $4300 ;Set DMA mode to fixed source, WORD to $2118/9 + LDX #$0000 + STX $2116 ;Set VRAM port address to $0000 + STX $0000 ;Set $00:0000 to $0000 (assumes scratchpad ram) + STX $4302 ;Set source address to $xx:0000 + LDA #$00 + STA $4304 ;Set source bank to $00 + LDX #$FFFF + STX $4305 ;Set transfer size to 64k-1 bytes + LDA #$01 + STA $420B ;Initiate transfer + + STZ $2119 ;clear the last byte of the VRAM + + plp + plx + pla + RTS + +;---------------------------------------------------------------------------- +; ClearPalette -- Reset all palette colors to zero +; In: None +; Out: None +; Modifies: flags +;---------------------------------------------------------------------------- +ClearPalette: + PHX + PHP + REP #$30 ; mem/A = 8 bit, X/Y = 16 bit + SEP #$20 + + STZ $2121 + LDX #$0100 +ClearPaletteLoop: + STZ $2122 + STZ $2122 + DEX + BNE ClearPaletteLoop + + PLP + PLX + RTS + +.ENDS + diff --git a/justfile b/justfile index 28e5492..dd26c15 100644 --- a/justfile +++ b/justfile @@ -1,6 +1,12 @@ default: just --list +simple_rom: + #!/usr/bin/env bash + cd simple-rom + wla-65816 -o simple_rom.obj simple_rom.asm + wlalink simple_rom.link simple_rom.smc + greenspace_smc: just legacy/greenspace/greenspace_smc diff --git a/simple-rom/header.inc b/simple-rom/header.inc new file mode 100644 index 0000000..a957351 --- /dev/null +++ b/simple-rom/header.inc @@ -0,0 +1,61 @@ +;------------------------------ Header File --------------------------------- +; This is basically a combo of MarctheMER's and Neviksti's header files +; Perhaps reading their's will also help your understanding of the header, +; but I believe this will be the simplest method of defining your header, +; as Marc's doesn't provide a full explanation, and Neviksti's can be +; a bit more difficult for beginners (using the WLA directives is easier). +;---------------------------------------------------------------------------- + +;==LoRom== ; We'll get to HiRom some other time. +.MEMORYMAP ; Begin describing the system architecture. + SLOTSIZE $8000 ; The slot is $8000 bytes in size. + DEFAULTSLOT 0 ; There's only 1 slot in SNES + SLOT 0 $8000 ; Define's Slot 0's starting address. +.ENDME ; End MemoryMap definition + +.ROMBANKSIZE $8000 ; Every ROM bank is 32 KBytes in size +.ROMBANKS 8 ; 2 Mbits - Tell WLA we want to use 8 ROM Banks + +.SNESHEADER + ID "SNES" ; 1-4 letter string, just leave it as "SNES" + + NAME "Test SNES ROM desu " ; Program Title - can't be over 21 bytes, + ; "123456789012345678901" ; use spaces for unused bytes of the name. + + SLOWROM + LOROM + + CARTRIDGETYPE $00 ; $00 = ROM only, see WLA documentation for others + ROMSIZE $08 ; $08 = 2 Mbits, see WLA doc for more.. + SRAMSIZE $00 ; No SRAM see WLA doc for more.. + COUNTRY $01 ; $01 = U.S. $00 = Japan, that's all I know + LICENSEECODE $00 ; Just use $00 + VERSION $00 ; $00 = 1.00, $01 = 1.01, etc. +.ENDSNES + +.SNESNATIVEVECTOR ; Define Native Mode interrupt vector table + COP EmptyHandler + BRK EmptyHandler + ABORT EmptyHandler + NMI EmptyHandler + IRQ EmptyHandler +.ENDNATIVEVECTOR + +.SNESEMUVECTOR ; Define Emulation Mode interrupt vector table + COP EmptyHandler + ABORT EmptyHandler + NMI EmptyHandler + RESET Start + IRQBRK EmptyHandler +.ENDEMUVECTOR + +.BANK 0 SLOT 0 ; Defines the ROM bank and the slot it is inserted in memory. +.ORG 0 ; .ORG 0 is really $8000, because the slot starts at $8000 +.SECTION "EmptyVectors" SEMIFREE + +EmptyHandler: + rti +.ENDS + +.EMPTYFILL $00 +;---------------------------------- END ------------------------------------- diff --git a/simple-rom/simple_rom.asm b/simple-rom/simple_rom.asm new file mode 100644 index 0000000..939547e --- /dev/null +++ b/simple-rom/simple_rom.asm @@ -0,0 +1,28 @@ +;== Include memorymap, header info, and SNES initialization routines +.INCLUDE "header.inc" +.INCLUDE "../common/InitSNES.asm" + +;======================== +; Start +;======================== + +.BANK 0 SLOT 0 +.ORG 0 +.SECTION "MainCode" + +Start: + InitSNES ; invoke SNES init + + stz $2121 ; set $2121 to zero, this sets palette color 0 + lda #%00010011 ; binary is more visual, but if you + sta $2122 ; Colors are 2 bytes. Write first byte from A + stz $2122 ; second byte is 0 + + lda #$0F ; = 00001111 + sta $2100 ; Turn on screen, full brightness + + +forever: + jmp forever + +.ENDS diff --git a/simple-rom/simple_rom.link b/simple-rom/simple_rom.link new file mode 100644 index 0000000..d02ce08 --- /dev/null +++ b/simple-rom/simple_rom.link @@ -0,0 +1,2 @@ +[objects] +simple_rom.obj