[PDF] Programming the SNES The structure of a SNES

ProgrammingtheSNES

Getoutofemulationmode.import native_reset;emu_reset:sei; disable interruptsclc;clear carry flagxce; switch to the native modeby swapping carry and emulation flagjmpnative_reset; •Wegottagetoutofthisplace..•The65816startsas6502clonein"emulationmode"•WejustswitchedfromNEStoSNEScapabilities

Welcometothemainroutinenative_reset:jsrforce_vblankjsrclear_snes; setup stack rep #$10 ; switch to 16bit mode .i16 ldx#$1FFF ; new stack pointer txssep#$10 ; switch to 8bit mode .i8 ; setup soft stack lda#<(__SOFTSTACK_START__ + __SOFTSTACK_SIZE__) stasp; write stack low bytelda#>(__SOFTSTACK_START__ + __SOFTSTACK_SIZE__) stasp+1 ; write stack high bytejsrrelocatedata; copy data from ROM to RAM jsr_set_slot; setup slot 0 -ignore this -my own framework blabla..: ; from now on every slot that returns ends up calling the next initldx#$00 jsr(current_init_slot,x); call initfrom C -ignore that there is some trampoline code involvedjsrend_force_vblank; and release vblank(stop forcing screen to black) cli ; enable interrupts againldx#$00 jsr(current_run_slot,x); call slot 0 run routinejsrforce_vblankbra :-; madness-do the same over and over again, but expect a different result.

AufeinemAugeblau-neuauchinC•Initandmainstructure•SettingRegisters(noDMA)// ...#define __REGB__(r) (*(volatile char*)((char)r))#define CGADD __REGB__(CGADD_ADDR)#define CGDATA __REGB__(CGDATA_ADDR)// ...void init(void){CGADD(0x00);// set a background colorCGDATA(0x3F);CGDATA(0x00);// ...Turn up brightness and enable NMI.}void run(void) {} // this is our main loop!void nmi(void) {}void irq(void) {} // you basically don't care about this one•Getabluescreen-Achievementunlocked!

WelcometotheworldofmagicnumbersinitDMATransfer();... addDMAChannel(0,0x18,current_bank,current_frame,4096,DMA_MODE_SHORT);addDMAChannel(1,0x22,0x66,current_clr,32,DMA_MODE_BYTE_TWICE);startDMATransfer();initHDMATransfer();...addHDMAChannel(2, 0x21, 0x44, &res_bg_table, 0, DMA_MODE_SHORT_TWICE);addHDMAChannel(3, 0x1B, angles[a].bank, angles[a].addr, 0, DMA_MODE_SHORT_TWICE);// ya, I know this one already addHDMAChannel(4, 0x1D, angles[a].bank+2, angles[a].addr, 0, DMA_MODE_SHORT_TWICE);// FIXME: needs checkingaddHDMAChannel(5, 0x05, 0, modeSwitchHdma, 0, DMA_MODE_BYTE);addHDMAChannel(6, 0x2C, 0, modeSwitch2Hdma, 0, DMA_MODE_BYTE);addHDMAChannel(7, 0x0D, 0, scrollSwitchHdma, 0, DMA_MODE_SHORT_TWICE);...startHDMATransfer();