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