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lsnes/bsnes-patches/v085/0027-Bus-fixes-Do-not-update-MDR-on-read-from-CPU-MMIO-sp.patch
Ilari Liusvaara f49b82c989 Bus fixes: Reading of CPU MMIO registers does not update MDR 
Also fixes controller timings to be more realistic.
2017-10-25 14:22:19 +03:00

377 lines
15 KiB
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Raw Blame History

From 4cfbbeadc3abe3e3911f7f59ce57b715edc76563 Mon Sep 17 00:00:00 2001
From: Ilari Liusvaara <ilariliusvaara@welho.com>
Date: Wed, 25 Oct 2017 14:18:34 +0300
Subject: [PATCH 27/27] Bus fixes: Do not update MDR on read from CPU MMIO
space
Also, updates the controller read timings to be more accurate.
---
snes/config/config.cpp | 1 +
snes/config/config.hpp | 1 +
snes/cpu/cpu.cpp | 2 +
snes/cpu/memory/memory.cpp | 26 ++++++++-
snes/cpu/mmio/mmio.cpp | 14 +++--
snes/cpu/timing/joypad.cpp | 132 +++++++++++++++++++++++++++++++++++++++------
snes/cpu/timing/timing.cpp | 11 ++--
snes/cpu/timing/timing.hpp | 3 +-
snes/snes.hpp | 1 +
9 files changed, 166 insertions(+), 25 deletions(-)
diff --git a/snes/config/config.cpp b/snes/config/config.cpp
index 19831370..8dcfd7e8 100755
--- a/snes/config/config.cpp
+++ b/snes/config/config.cpp
@@ -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;
diff --git a/snes/config/config.hpp b/snes/config/config.hpp
index 68fe0bde..d8577e39 100755
--- a/snes/config/config.hpp
+++ b/snes/config/config.hpp
@@ -14,6 +14,7 @@ struct Configuration {
unsigned pal_frequency;
unsigned wram_init_value;
bool alt_poll_timings;
+ bool bus_fixes;
} cpu;
struct SMP {
diff --git a/snes/cpu/cpu.cpp b/snes/cpu/cpu.cpp
index e11fc882..5e8e3137 100755
--- a/snes/cpu/cpu.cpp
+++ b/snes/cpu/cpu.cpp
@@ -1,5 +1,7 @@
#include <snes/snes.hpp>
#include <cstdio>
+#include <iostream>
+#include <cassert>
#define CPU_CPP
namespace SNES {
diff --git a/snes/cpu/memory/memory.cpp b/snes/cpu/memory/memory.cpp
index 31f82c31..df439c22 100755
--- a/snes/cpu/memory/memory.cpp
+++ b/snes/cpu/memory/memory.cpp
@@ -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) {
diff --git a/snes/cpu/mmio/mmio.cpp b/snes/cpu/mmio/mmio.cpp
index 30048c19..be2990a3 100755
--- a/snes/cpu/mmio/mmio.cpp
+++ b/snes/cpu/mmio/mmio.cpp
@@ -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
diff --git a/snes/cpu/timing/joypad.cpp b/snes/cpu/timing/joypad.cpp
index afca7504..b60be020 100755
--- a/snes/cpu/timing/joypad.cpp
+++ b/snes/cpu/timing/joypad.cpp
@@ -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;
}
}
diff --git a/snes/cpu/timing/timing.cpp b/snes/cpu/timing/timing.cpp
index d7cf24f3..ef81d891 100755
--- a/snes/cpu/timing/timing.cpp
+++ b/snes/cpu/timing/timing.cpp
@@ -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;
}
diff --git a/snes/cpu/timing/timing.hpp b/snes/cpu/timing/timing.hpp
index bf15a727..8be2b830 100755
--- a/snes/cpu/timing/timing.hpp
+++ b/snes/cpu/timing/timing.hpp
@@ -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);
diff --git a/snes/snes.hpp b/snes/snes.hpp
index 3a65e360..961842b3 100755
--- a/snes/snes.hpp
+++ b/snes/snes.hpp
@@ -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
--
2.15.0.rc1
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