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-rw-r--r--genesis.c6
-rw-r--r--io.c71
-rw-r--r--io.h2
3 files changed, 73 insertions, 6 deletions
diff --git a/genesis.c b/genesis.c
index ff14c36..635965b 100644
--- a/genesis.c
+++ b/genesis.c
@@ -513,13 +513,13 @@ static m68k_context * io_write(uint32_t location, m68k_context * context, uint8_
io_data_write(gen->io.ports+2, value, context->current_cycle);
break;
case 0x4:
- gen->io.ports[0].control = value;
+ io_control_write(gen->io.ports, value, context->current_cycle);
break;
case 0x5:
- gen->io.ports[1].control = value;
+ io_control_write(gen->io.ports+1, value, context->current_cycle);
break;
case 0x6:
- gen->io.ports[2].control = value;
+ io_control_write(gen->io.ports+2, value, context->current_cycle);
break;
case 0x7:
gen->io.ports[0].serial_out = value;
diff --git a/io.c b/io.c
index 3769ac8..b6ecabe 100644
--- a/io.c
+++ b/io.c
@@ -1506,6 +1506,16 @@ void io_adjust_cycles(io_port * port, uint32_t current_cycle, uint32_t deduction
port->device.mouse.ready_cycle -= deduction;
}
}
+ for (int i = 0; i < 8; i++)
+ {
+ if (port->slow_rise_start[i] != CYCLE_NEVER) {
+ if (port->slow_rise_start[i] >= deduction) {
+ port->slow_rise_start[i] -= deduction;
+ } else {
+ port->slow_rise_start[i] = CYCLE_NEVER;
+ }
+ }
+ }
if (last_poll_cycle >= deduction) {
last_poll_cycle -= deduction;
} else {
@@ -1623,6 +1633,25 @@ enum {
KB_WRITE
};
+void io_control_write(io_port *port, uint8_t value, uint32_t current_cycle)
+{
+ uint8_t changes = value ^ port->control;
+ if (changes) {
+ for (int i = 0; i < 8; i++)
+ {
+ if (!(value & 1 << i) && !(port->output & 1 << i)) {
+ //port switched from output to input and the output value was 0
+ //since there is a weak pull-up on input pins, this will lead
+ //to a slow rise from 0 to 1 if the pin isn't being externally driven
+ port->slow_rise_start[i] = current_cycle;
+ } else {
+ port->slow_rise_start[i] = CYCLE_NEVER;
+ }
+ }
+ port->control = value;
+ }
+}
+
void io_data_write(io_port * port, uint8_t value, uint32_t current_cycle)
{
uint8_t old_output = (port->control & port->output) | (~port->control & 0xFF);
@@ -1766,12 +1795,34 @@ uint8_t get_scancode_bytes(io_port *port)
return bytes;
}
+#define SLOW_RISE_DEVICE (30*7)
+#define SLOW_RISE_INPUT (12*7)
+
+static uint8_t get_output_value(io_port *port, uint32_t current_cycle, uint32_t slow_rise_delay)
+{
+ uint8_t output = (port->control | 0x80) & port->output;
+ for (int i = 0; i < 8; i++)
+ {
+ if (!(port->control & 1 << i)) {
+ if (port->slow_rise_start[i] != CYCLE_NEVER) {
+ if (current_cycle - port->slow_rise_start[i] >= slow_rise_delay) {
+ output |= 1 << i;
+ }
+ } else {
+ output |= 1 << i;
+ }
+ }
+ }
+ return output;
+}
+
uint8_t io_data_read(io_port * port, uint32_t current_cycle)
{
+ uint8_t output = get_output_value(port, current_cycle, SLOW_RISE_DEVICE);
uint8_t control = port->control | 0x80;
- uint8_t output = (control & port->output) | (~control & 0xFF);
uint8_t th = output & 0x40;
uint8_t input;
+ uint8_t device_driven;
if (current_cycle - last_poll_cycle > MIN_POLL_INTERVAL) {
process_events();
last_poll_cycle = current_cycle;
@@ -1789,6 +1840,7 @@ uint8_t io_data_read(io_port * port, uint32_t current_cycle)
}
//controller output is logically inverted
input = ~input;
+ device_driven = 0x3F;
break;
}
case IO_GAMEPAD6:
@@ -1816,6 +1868,7 @@ uint8_t io_data_read(io_port * port, uint32_t current_cycle)
}
//controller output is logically inverted
input = ~input;
+ device_driven = 0x3F;
break;
}
case IO_MOUSE:
@@ -1875,6 +1928,7 @@ uint8_t io_data_read(io_port * port, uint32_t current_cycle)
}
input |= ((port->device.mouse.tr_counter & 1) == 0) << 4;
}
+ device_driven = 0x1F;
break;
}
case IO_SATURN_KEYBOARD:
@@ -1947,6 +2001,7 @@ uint8_t io_data_read(io_port * port, uint32_t current_cycle)
}
input |= ((port->device.keyboard.tr_counter & 1) == 0) << 4;
}
+ device_driven = 0x1F;
break;
}
case IO_XBAND_KEYBOARD:
@@ -2008,6 +2063,8 @@ uint8_t io_data_read(io_port * port, uint32_t current_cycle)
input = 0xF;
}
input |= ((port->device.keyboard.tr_counter & 1) == 0) << 4;
+ //this is not strictly correct at all times, but good enough for now
+ device_driven = 0x1F;
}
break;
}
@@ -2018,6 +2075,7 @@ uint8_t io_data_read(io_port * port, uint32_t current_cycle)
service_pipe(port);
}
input = port->input[th ? IO_TH1 : IO_TH0];
+ device_driven = 0x3F;
break;
case IO_GENERIC:
if (port->input[IO_TH0] & 0x80 && port->input[IO_STATE] == IO_WRITTEN)
@@ -2027,13 +2085,20 @@ uint8_t io_data_read(io_port * port, uint32_t current_cycle)
}
service_socket(port);
input = port->input[IO_TH0];
+ device_driven = 0x7F;
break;
#endif
default:
- input = 0xFF;
+ input = 0;
+ device_driven = 0;
break;
}
- uint8_t value = (input & (~control)) | (port->output & control);
+ uint8_t value = (input & (~control) & device_driven) | (port->output & control);
+ //deal with pins that are configured as inputs, but not being actively driven by the device
+ uint8_t floating = (~device_driven) & (~control);
+ if (floating) {
+ value |= get_output_value(port, current_cycle, SLOW_RISE_INPUT) & floating;
+ }
/*if (port->input[GAMEPAD_TH0] || port->input[GAMEPAD_TH1]) {
printf ("value: %X\n", value);
}*/
diff --git a/io.h b/io.h
index 958ffc8..5814c7a 100644
--- a/io.h
+++ b/io.h
@@ -60,6 +60,7 @@ typedef struct {
uint8_t output;
uint8_t control;
uint8_t input[3];
+ uint32_t slow_rise_start[8];
uint8_t serial_out;
uint8_t serial_in;
uint8_t serial_ctrl;
@@ -95,6 +96,7 @@ void set_keybindings(sega_io *io);
void map_all_bindings(sega_io *io);
void setup_io_devices(tern_node * config, rom_info *rom, sega_io *io);
void io_adjust_cycles(io_port * pad, uint32_t current_cycle, uint32_t deduction);
+void io_control_write(io_port *port, uint8_t value, uint32_t current_cycle);
void io_data_write(io_port * pad, uint8_t value, uint32_t current_cycle);
uint8_t io_data_read(io_port * pad, uint32_t current_cycle);
void handle_keydown(int keycode, uint8_t scancode);
generated by cgit v1.2.3 (git 2.25.1) at 2025-06-19 20:14:12 +0000