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Implement RTC #1

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paoda merged 14 commits from rtc into main 2022-09-17 23:36:34 +00:00
Conversation 0 Commits 14 Files Changed 8 +52 -75
1 changed files with 52 additions and 75 deletions
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127
src/core/bus/GamePak.zig
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@ -318,7 +318,6 @@ const Gpio = struct {
const Clock = struct { const Clock = struct {
const This = @This(); const This = @This();
cmd: Command,
writer: Writer, writer: Writer,
reader: Reader, reader: Reader,
state: State, state: State,
@ -343,7 +342,7 @@ const Clock = struct {
const State = union(enum) { const State = union(enum) {
Idle, Idle,
CommandInput, Command,
Write: Register, Write: Register,
Read: Register, Read: Register,
}; };
@ -499,72 +498,6 @@ const Clock = struct {
} }
}; };
const Command = struct {
buf: u8,
i: u4,
fn write(self: *Command, value: u1) void {
const idx = @intCast(u3, self.i);
self.buf = (self.buf & ~(@as(u8, 1) << idx)) | @as(u8, value) << idx;
self.i += 1;
}
fn reset(self: *Command) void {
self.buf = 0;
self.i = 0;
}
fn isFinished(self: *const Command) bool {
return self.i >= 8;
}
fn getCommand(self: *const Command) u8 {
// If High Nybble is 0x6, no need to switch the endianness
if (self.buf >> 4 & 0xF == 0x6) return self.buf;
// Turns out reversing the order of bits isn't trivial at all
// https://stackoverflow.com/questions/2602823/in-c-c-whats-the-simplest-way-to-reverse-the-order-of-bits-in-a-byte
var ret = self.buf;
ret = (ret & 0xF0) >> 4 | (ret & 0x0F) << 4;
ret = (ret & 0xCC) >> 2 | (ret & 0x33) << 2;
ret = (ret & 0xAA) >> 1 | (ret & 0x55) << 1;
return ret;
}
fn handleCommand(self: *const Command, rtc: *Clock) State {
const command = self.getCommand();
log.debug("RTC: Handling Command 0x{X:0>2} [0b{b:0>8}]", .{ command, command });
const is_write = command & 1 == 0;
const rtc_register = @truncate(u3, command >> 1 & 0x7);
if (is_write) {
return switch (rtc_register) {
0 => blk: {
rtc.reset();
break :blk .Idle;
},
1 => .{ .Write = .Control },
2 => .{ .Write = .DateTime },
3 => .{ .Write = .Time },
6 => blk: {
rtc.irq();
break :blk .Idle;
},
4, 5, 7 => .Idle,
};
} else {
return switch (rtc_register) {
1 => .{ .Read = .Control },
2 => .{ .Read = .DateTime },
3 => .{ .Read = .Time },
0, 4, 5, 6, 7 => .Idle, // Do Nothing
};
}
}
};
const Data = extern union { const Data = extern union {
sck: Bit(u8, 0), sck: Bit(u8, 0),
sio: Bit(u8, 1), sio: Bit(u8, 1),
@ -590,7 +523,6 @@ const Clock = struct {
fn init(ptr: *This, cpu: *Arm7tdmi, gpio: *const Gpio) void { fn init(ptr: *This, cpu: *Arm7tdmi, gpio: *const Gpio) void {
ptr.* = .{ ptr.* = .{
.cmd = .{ .buf = 0, .i = 0 },
.writer = .{ .buf = 0, .i = 0, .count = 0 }, .writer = .{ .buf = 0, .i = 0, .count = 0 },
.reader = .{ .i = 0, .count = 0 }, .reader = .{ .i = 0, .count = 0 },
.state = .Idle, .state = .Idle,
@ -616,22 +548,23 @@ const Clock = struct {
if (cache.sck.read()) { if (cache.sck.read()) {
if (!cache.cs.read() and value.cs.read()) { if (!cache.cs.read() and value.cs.read()) {
log.debug("RTC: Entering Command Mode", .{}); log.debug("RTC: Entering Command Mode", .{});
self.state = .CommandInput; self.state = .Command;
self.cmd.reset();
} }
} }
break :blk @truncate(u4, value.raw); break :blk @truncate(u4, value.raw);
}, },
.CommandInput => blk: { .Command => blk: {
if (!value.cs.read()) log.err("RTC: Expected CS to be set during {}, however CS was cleared", .{self.state}); if (!value.cs.read()) log.err("RTC: Expected CS to be set during {}, however CS was cleared", .{self.state});
// If SCK rises, sample SIO // If SCK rises, sample SIO
if (!cache.sck.read() and value.sck.read()) { if (!cache.sck.read() and value.sck.read()) {
self.cmd.write(@boolToInt(value.sio.read())); self.writer.push(@boolToInt(value.sio.read()));
if (self.writer.finished()) {
self.state = self.processCommand(self.writer.buf);
self.writer.reset();
if (self.cmd.isFinished()) {
self.state = self.cmd.handleCommand(self);
log.debug("RTC: Switching to {}", .{self.state}); log.debug("RTC: Switching to {}", .{self.state});
} }
} }
@ -707,4 +640,48 @@ const Clock = struct {
self.cpu.bus.io.irq.game_pak.set(); self.cpu.bus.io.irq.game_pak.set();
self.cpu.handleInterrupt(); self.cpu.handleInterrupt();
} }
fn processCommand(self: *This, raw_command: u8) State {
const command = blk: {
// If High Nybble is 0x6, no need to switch the endianness
if (raw_command >> 4 & 0xF == 0x6) break :blk raw_command;
// Turns out reversing the order of bits isn't trivial at all
// https://stackoverflow.com/questions/2602823/in-c-c-whats-the-simplest-way-to-reverse-the-order-of-bits-in-a-byte
var ret = raw_command;
ret = (ret & 0xF0) >> 4 | (ret & 0x0F) << 4;
ret = (ret & 0xCC) >> 2 | (ret & 0x33) << 2;
ret = (ret & 0xAA) >> 1 | (ret & 0x55) << 1;
break :blk ret;
};
log.debug("RTC: Handling Command 0x{X:0>2} [0b{b:0>8}]", .{ command, command });
const is_write = command & 1 == 0;
const rtc_register = @truncate(u3, command >> 1 & 0x7);
if (is_write) {
return switch (rtc_register) {
0 => blk: {
self.reset();
break :blk .Idle;
},
1 => .{ .Write = .Control },
2 => .{ .Write = .DateTime },
3 => .{ .Write = .Time },
6 => blk: {
self.irq();
break :blk .Idle;
},
4, 5, 7 => .Idle,
};
} else {
return switch (rtc_register) {
1 => .{ .Read = .Control },
2 => .{ .Read = .DateTime },
3 => .{ .Read = .Time },
0, 4, 5, 6, 7 => .Idle, // Do Nothing
};
}
}
}; };