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Bus fixes: Do not update MDR on read from CPU MMIO space

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Also, updates the controller read timings to be more accurate.
This commit is contained in:
Ilari Liusvaara 2017-10-25 14:18:34 +03:00
parent c0a2270cfd
commit 4cfbbeadc3
9 changed files with 166 additions and 25 deletions
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1
snes/config/config.cpp
View file

@ -15,6 +15,7 @@ Configuration::Configuration() {
cpu.pal_frequency = 21281370;
cpu.wram_init_value = 0x55;
cpu.alt_poll_timings = false;
cpu.bus_fixes = false;
smp.ntsc_frequency = 24607104; //32040.5 * 768
smp.pal_frequency = 24607104;

1
snes/config/config.hpp
View file

@ -14,6 +14,7 @@ struct Configuration {
unsigned pal_frequency;
unsigned wram_init_value;
bool alt_poll_timings;
bool bus_fixes;
} cpu;
struct SMP {

2
snes/cpu/cpu.cpp
View file

@ -1,5 +1,7 @@
#include <snes/snes.hpp>
#include <cstdio>
#include <iostream>
#include <cassert>
#define CPU_CPP
namespace SNES {

26
snes/cpu/memory/memory.cpp
View file

@ -14,10 +14,32 @@ uint8 CPU::op_read(uint32 addr, bool exec) {
status.clock_count = speed(addr);
dma_edge();
add_clocks(status.clock_count - 4);
regs.mdr = bus.read(addr, exec);
//MDR presents the state held by parasitic capacitance of the external bus.
//This bus is not affected by reads from CPU-internal registers, only if
//some external device responds. SDD1 does hook some of these addresses, but
//passes read straight through, as expected (as the CPU probably won't
//monitor if external device responds, even if it broadcasts a read).
//
//We use 4000-43FF as CPU register range, and not 4000-437F it likely is
//for quickness of checking. This will only affect things if some device
//tries to map the 4380-43FF range (that device will still work correctly,
//but openbus in that range won't).
//
//This was discovered while investigating why one Super Metroid glitch
//worked on emulator but crashed on real console.
//
//a word fetch from 2f4017 AND 0xfffc results in 2f3c and a word fetch from
//2f4210 AND 0x7f7f results in 2f22. This also extends to long fetches
//by arguments. E.g. long argument fetch from 94420F with 2F already on
//the bus AND 0x7f7fff results in 2f222f.
//
//The reason for masking some bits in above explanation was to ignore some
//known bits in those registers (bits 7 of 4210 and 4211, bits 0&1 of 4017).
uint8_t tmp = bus.read(addr, exec);
if(!config.cpu.bus_fixes || (addr & 0x40FC00) != 0x004000) regs.mdr = tmp;
add_clocks(4);
alu_edge();
return regs.mdr;
return tmp;
}
void CPU::op_write(uint32 addr, uint8 data) {

14
snes/cpu/mmio/mmio.cpp
View file

@ -33,9 +33,17 @@ void CPU::mmio_w2183(uint8 data) {
//strobing $4016.d0 affects both controller port latches.
//$4017 bit 0 writes are ignored.
void CPU::mmio_w4016(uint8 data) {
if(data&1) interface->notifyLatched();
input.port1->latch(data & 1);
input.port2->latch(data & 1);
//Only consider autoassert if both busfix and auto flags are set.
auto auto_asserted = (status.auto_joypad_counter & 384) == 384;
//Bit 6 of status.auto_joypad_counter follows "manual" latch.
auto oldstatus = auto_asserted || (status.auto_joypad_counter & 64) != 0;
status.auto_joypad_counter &= ~64;
status.auto_joypad_counter |= (data & 1) << 6;
auto newstatus = auto_asserted || (status.auto_joypad_counter & 64) != 0;
//If !oldstatus and newstatus, signal latch.
if(!oldstatus && newstatus) interface->notifyLatched();
input.port1->latch(newstatus);
input.port2->latch(newstatus);
}
//JOYSER0

132
snes/cpu/timing/joypad.cpp
View file

@ -3,11 +3,14 @@
//called every 256 clocks; see CPU::add_clocks()
void CPU::step_auto_joypad_poll() {
if(vcounter() >= (ppu.overscan() == false ? 225 : 240)) {
auto cycle = status.auto_joypad_counter & 63;
//cache enable state at first iteration
if(status.auto_joypad_counter == 0) status.auto_joypad_latch = status.auto_joypad_poll;
status.auto_joypad_active = status.auto_joypad_counter <= 15;
if(cycle == 0) status.auto_joypad_latch = status.auto_joypad_poll;
status.auto_joypad_active = cycle <= 15;
if(status.auto_joypad_active && status.auto_joypad_latch) {
if(status.auto_joypad_counter == 0) {
if(cycle == 0) {
if(status.auto_joypad_counter & 128)
std::cerr << "step_auto_joypad_poll(): bus fixes set (counter=" << status.auto_joypad_counter << ")???" << std::endl;
if(dma_trace_fn) dma_trace_fn("-- Start automatic polling --");
interface->notifyLatched();
input.port1->latch(1);
@ -23,7 +26,7 @@ void CPU::step_auto_joypad_poll() {
status.joy2 = (status.joy2 << 1) | (bool)(port1 & 1);
status.joy3 = (status.joy3 << 1) | (bool)(port0 & 2);
status.joy4 = (status.joy4 << 1) | (bool)(port1 & 2);
if(status.auto_joypad_counter == 15) {
if(cycle == 15) {
char buf[512];
sprintf(buf, "-- End automatic polling [%04x %04x %04x %04x] --",
status.joy1, status.joy2, status.joy3, status.joy4);
@ -31,32 +34,129 @@ void CPU::step_auto_joypad_poll() {
}
}
status.auto_joypad_counter++;
//Only bits 0-5 are supposed to increment.
if(cycle < 60)
status.auto_joypad_counter++;
}
}
//called every 128 clocks; see CPU::add_clocks()
void CPU::step_auto_joypad_poll_NEW(bool polarity) {
if(status.auto_joypad_counter > 0 && status.auto_joypad_counter <= 34) {
void CPU::step_auto_joypad_poll_NEW2(bool polarity) {
//Poll starts on multiple of 128 mod 256 clocks (polarity=false) on first
//vblank scanline. If autopoller is off, mark as done for the frame.
if(vcounter() >= (ppu.overscan() == false ? 225 : 240) && !polarity &&
(status.auto_joypad_counter & 63) == 0) {
if(!(status.auto_joypad_counter & 128))
std::cerr << "step_auto_joypad_poll_NEW2(): bus fixes clear???" << std::endl;
//Preserve high bits of autopoll counter.
auto x = status.auto_joypad_counter & ~63;
status.auto_joypad_counter = x | (status.auto_joypad_poll ? 1 : 36);
status.auto_joypad_latch = status.auto_joypad_poll;
}
//Abuse bit 6 of counter for "manual" poll flag. Bit 7 is supposed to be
//always set.
auto cycle = status.auto_joypad_counter & 63;
auto old_latchstate = (status.auto_joypad_counter & 320) != 0;
//If not enabled... This is not latched, as autopoll can be aborted.
if(!status.auto_joypad_poll && cycle > 0 && cycle < 36) {
if(dma_trace_fn) dma_trace_fn("-- Automatic polling ABORTED --");
status.auto_joypad_counter += (36 - cycle);
status.auto_joypad_active = false;
status.auto_joypad_latch = false;
//Release autopoll latch.
status.auto_joypad_counter &= ~256; //Autopoll clears latch.
auto new_latchstate = (status.auto_joypad_counter & 320) != 0;
if(old_latchstate && !new_latchstate) {
input.port1->latch(0);
input.port2->latch(0);
}
return;
}
//On cycle #1, latch is asserted (unless latch is already high, in this
//case the autopoller is supposed to force latch high too).
if(cycle == 1) {
if(dma_trace_fn) dma_trace_fn("-- Start automatic polling --");
//Assert autopoll latch.
status.auto_joypad_counter |= 256;
auto new_latchstate = (status.auto_joypad_counter & 320) != 0;
if(!old_latchstate && new_latchstate) {
interface->notifyLatched();
input.port1->latch(1);
input.port2->latch(1);
}
}
//On cycle #2, busy is asserted and controllers are cleared.
if(cycle == 2) {
status.joy1 = 0;
status.joy2 = 0;
status.joy3 = 0;
status.joy4 = 0;
status.auto_joypad_active = true;
}
//Then, on cycle #3, latch is deasserted, unless "manual" latch forces
//real latch high.
if(cycle == 3) {
//Release autopoll latch.
status.auto_joypad_counter &= ~256;
auto new_latchstate = (status.auto_joypad_counter & 320) != 0;
if(old_latchstate && !new_latchstate) {
input.port1->latch(0);
input.port2->latch(0);
}
}
//Then on cycles #4, #6, #8, ..., #34, a bit is shifted. Also, clock would
//go low, but we can not emulate that.
if(cycle >= 4 && cycle <= 34 && cycle % 2 == 0) {
uint2 port0 = input.port1->data();
uint2 port1 = input.port2->data();
status.joy1 = (status.joy1 << 1) | (bool)(port0 & 1);
status.joy2 = (status.joy2 << 1) | (bool)(port1 & 1);
status.joy3 = (status.joy3 << 1) | (bool)(port0 & 2);
status.joy4 = (status.joy4 << 1) | (bool)(port1 & 2);
}
//Then on cycles #5, #7, #9, ..., #35, clock drops high, But we can not
//emulate that.
//Then on cycle #35, busy flag is deasserted and poll is complete.
if(cycle == 35) {
status.auto_joypad_active = false;
char buf[512];
sprintf(buf, "-- End automatic polling [%04x %04x %04x %04x] --",
status.joy1, status.joy2, status.joy3, status.joy4);
if(dma_trace_fn) dma_trace_fn(buf);
}
//The entiere train is 35 cycles.
if(cycle > 0 && cycle < 36) {
status.auto_joypad_counter++;
}
}
//called every 128 clocks; see CPU::add_clocks()
void CPU::step_auto_joypad_poll_NEW(bool polarity, bool new2) {
if(new2) return step_auto_joypad_poll_NEW2(polarity);
auto cycle = status.auto_joypad_counter & 63;
if(cycle > 0 && cycle <= 34) {
if(!status.auto_joypad_latch) {
//FIXME: Is this right, busy flag goes on even if not enabled???
if(status.auto_joypad_counter == 1)
if(cycle == 1)
status.auto_joypad_active = true;
if(status.auto_joypad_counter == 34)
if(cycle == 34)
status.auto_joypad_active = false;
} else {
if(status.auto_joypad_counter == 1) {
if(cycle == 1) {
if(status.auto_joypad_counter & 128)
std::cerr << "step_auto_joypad_poll_NEW(): bus fixes set???" << std::endl;
if(dma_trace_fn) dma_trace_fn("-- Start automatic polling --");
status.auto_joypad_active = true;
interface->notifyLatched();
input.port1->latch(1);
input.port2->latch(1);
}
if(status.auto_joypad_counter == 3) {
if(cycle == 3) {
input.port1->latch(0);
input.port2->latch(0);
}
if((status.auto_joypad_counter & 1) != 0 && status.auto_joypad_counter != 1) {
if((cycle & 1) != 0 && cycle != 1) {
uint2 port0 = input.port1->data();
uint2 port1 = input.port2->data();
@ -65,7 +165,7 @@ void CPU::step_auto_joypad_poll_NEW(bool polarity) {
status.joy3 = (status.joy3 << 1) | (bool)(port0 & 2);
status.joy4 = (status.joy4 << 1) | (bool)(port1 & 2);
}
if(status.auto_joypad_counter == 34) {
if(cycle == 34) {
status.auto_joypad_active = false;
char buf[512];
sprintf(buf, "-- End automatic polling [%04x %04x %04x %04x] --",
@ -75,9 +175,11 @@ void CPU::step_auto_joypad_poll_NEW(bool polarity) {
}
status.auto_joypad_counter++;
}
if(vcounter() >= (ppu.overscan() == false ? 225 : 240) && status.auto_joypad_counter == 0 && !polarity) {
if(vcounter() >= (ppu.overscan() == false ? 225 : 240) && cycle == 0 && !polarity) {
//Preserve high bits of autopoller counter.
auto x = status.auto_joypad_counter & ~63;
status.auto_joypad_latch = status.auto_joypad_poll;
status.auto_joypad_counter = 1;
status.auto_joypad_counter = x | 1;
}
}

11
snes/cpu/timing/timing.cpp
View file

@ -17,12 +17,12 @@ void CPU::add_clocks(unsigned clocks) {
step(clocks);
if(config.cpu.alt_poll_timings) {
if(config.cpu.alt_poll_timings || config.cpu.bus_fixes) {
bool opolarity = (status.auto_joypad_clock & 128);
status.auto_joypad_clock = (status.auto_joypad_clock + clocks) & 0xFF;
bool npolarity = (status.auto_joypad_clock & 128);
if(opolarity != npolarity)
step_auto_joypad_poll_NEW(opolarity);
step_auto_joypad_poll_NEW(opolarity, config.cpu.bus_fixes);
} else {
status.auto_joypad_clock += clocks;
if(status.auto_joypad_clock >= 256) {
@ -53,7 +53,8 @@ void CPU::scanline() {
status.hdma_init_position = (cpu_version == 1 ? 12 + 8 - dma_counter() : 12 + dma_counter());
status.hdma_init_triggered = false;
status.auto_joypad_counter = 0;
//Only clear the low 6 bits (counter).
status.auto_joypad_counter &= ~63;
}
//DRAM refresh occurs once every scanline
@ -200,7 +201,9 @@ void CPU::timing_reset() {
status.auto_joypad_active = false;
status.auto_joypad_latch = false;
status.auto_joypad_counter = 0;
//Set bit 7 of joypad counter if bus fixes are active (for combined
//latch behavior).
status.auto_joypad_counter = config.cpu.bus_fixes ? 128 : 0;
status.auto_joypad_clock = 0;
}

3
snes/cpu/timing/timing.hpp
View file

@ -22,4 +22,5 @@ alwaysinline bool irq_test();
//joypad.cpp
void step_auto_joypad_poll();
void step_auto_joypad_poll_NEW(bool polarity);
void step_auto_joypad_poll_NEW(bool polarity, bool new2);
void step_auto_joypad_poll_NEW2(bool polarity);

1
snes/snes.hpp
View file

@ -3,6 +3,7 @@
#define BSNES_SUPPORTS_ADV_BREAKPOINTS
#define BSNES_SUPPORTS_ADV_BREAKPOINTS_PPU
#define BSNES_SUPPORTS_ALT_TIMINGS
#define BSNES_SUPPORTS_BUS_FIXES
#define BSNES_SUPPORTS_TRACE_SA1
#define BSNES_SUPPORTS_DMA_TRACE