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Introduces horizontal counter latching and reading.

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Then makes a new guess at frame IRQ position. But gets it wrong. Hmmm.
This commit is contained in:
Thomas Harte
2018-10-11 19:56:32 -04:00
parent 9a933993f5
commit 52e02db5c8
4 changed files with 61 additions and 10 deletions
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43
Machines/MasterSystem/MasterSystem.cpp
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@@ -184,10 +184,13 @@ class ConcreteMachine:
printf("TODO: [input] I/O port control\n");
*cycle.value = 0xff;
break;
case 0x40: case 0x41:
case 0x40:
update_video();
*cycle.value = vdp_->get_current_line();
break;
case 0x41:
*cycle.value = vdp_->get_latched_horizontal_counter();
break;
case 0x80: case 0x81:
update_video();
*cycle.value = vdp_->get_register(address);
@@ -201,7 +204,11 @@ class ConcreteMachine:
} break;
case 0xc1: {
Joystick *const joypad2 = static_cast<Joystick *>(joysticks_[1].get());
*cycle.value = (joypad2->get_state() >> 2) | 0xf;
*cycle.value =
(joypad2->get_state() >> 2) |
0x30 |
get_th_values();
} break;
default:
@@ -219,9 +226,20 @@ class ConcreteMachine:
page_cartridge();
}
break;
case 0x01:
printf("TODO: [output] I/O port control\n");
break;
case 0x01: {
// A programmer can force the TH lines to 0 here,
// causing a phoney lightgun latch, so check for any
// discontinuity in TH inputs.
const auto previous_ths = get_th_values();
io_port_control_ = *cycle.value;
const auto new_ths = get_th_values();
// Latch if either TH has newly gone to 1.
if((new_ths^previous_ths)&new_ths) {
update_video();
vdp_->latch_horizontal_counter();
}
} break;
case 0x40: case 0x41:
update_audio();
sn76489_.set_register(*cycle.value);
@@ -233,7 +251,7 @@ class ConcreteMachine:
time_until_interrupt_ = vdp_->get_time_until_interrupt();
break;
case 0xc0:
// printf("TODO: [output] I/O port A/N [%02x]\n", *cycle.value);
printf("TODO: [output] I/O port A/N [%02x]\n", *cycle.value);
break;
case 0xc1:
printf("TODO: [output] I/O port B/misc\n");
@@ -274,6 +292,17 @@ class ConcreteMachine:
}
private:
inline uint8_t get_th_values() {
// Quick not on TH inputs here: if either is setup as an output, then the
// currently output level is returned. Otherwise they're fixed at 1.
return
static_cast<uint8_t>(
((io_port_control_ & 0x02) << 5) | ((io_port_control_&0x20) << 1) |
((io_port_control_ & 0x08) << 4) | (io_port_control_&0x80)
);
}
inline void update_audio() {
speaker_.run_for(audio_queue_, time_since_sn76489_update_.divide_cycles(Cycles(sn76489_divider)));
}
@@ -299,6 +328,8 @@ class ConcreteMachine:
uint8_t bios_[8*1024];
std::vector<uint8_t> cartridge_;
uint8_t io_port_control_ = 0x0f;
// The memory map has a 1kb granularity; this is determined by the SG1000's 1kb of RAM.
const uint8_t *read_pointers_[64];
uint8_t *write_pointers_[64];