Added RTC

Added I/O waits to PIC remapping

Added fmt step to build 

When building will format all the code to the standard

Fixed cascading interrupts

Re-named to selectAnd*Register. Moved switching on registers into emun


Removed build fmt step

src/kernel/arch/x86/arch.zig

@@ -7,6 +7,7 @@ const pic = @import("pic.zig");
 const irq = @import("irq.zig");
 const isr = @import("isr.zig");
 const pit = @import("pit.zig");
+const rtc = @import("rtc.zig");
 const paging = @import("paging.zig");
 const syscalls = @import("syscalls.zig");
 const mem = @import("../../mem.zig");
@@ -81,6 +82,13 @@ pub fn inb(port: u16) u8 {
     );
 }
 
+///
+/// Force the CPU to wait for an I/O operation to compete. Use port 0x80 as this is unused.
+///
+pub fn ioWait() void {
+    outb(0x80, 0);
+}
+
 ///
 /// Load the GDT and refreshing the code segment with the code segment offset of the kernel as we
 /// are still in kernel land. Also loads the kernel data segment into all the other segment
@@ -230,10 +238,11 @@ pub fn init(mb_info: *multiboot.multiboot_info_t, mem_profile: *const MemProfile
     isr.init();
     irq.init();
 
-    pit.init();
-
     paging.init(mb_info, mem_profile, allocator);
 
+    pit.init();
+    rtc.init();
+
     syscalls.init();
 
     enableInterrupts();
@@ -246,6 +255,8 @@ test "" {
     _ = @import("isr.zig");
     _ = @import("irq.zig");
     _ = @import("pit.zig");
+    _ = @import("cmos.zig");
+    _ = @import("rtc.zig");
     _ = @import("syscalls.zig");
     _ = @import("paging.zig");
 }

src/kernel/arch/x86/cmos.zig

@@ -0,0 +1,463 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const is_test = builtin.is_test;
+const expectEqual = std.testing.expectEqual;
+const build_options = @import("build_options");
+const mock_path = build_options.arch_mock_path;
+const arch = if (is_test) @import(mock_path ++ "arch_mock.zig") else @import("arch.zig");
+
+/// The current year to be used for calculating the 4 digit year, as the CMOS return the last two
+/// digits of the year.
+const CURRENT_CENTURY: u8 = 2000;
+
+/// The port address for the CMOS command register.
+const ADDRESS: u16 = 0x70;
+
+/// The port address for the CMOS data register.
+const DATA: u16 = 0x71;
+
+/// The register location for returning the seconds, (0 - 59).
+const REGISTER_SECOND: u8 = 0x00;
+
+/// The register location for returning the minute, (0 - 59).
+const REGISTER_MINUTE: u8 = 0x02;
+
+/// The register location for returning the hours, (0 - 23 or 0 - 12 depending if a 12hr or 24hr
+/// clock).
+const REGISTER_HOUR: u8 = 0x04;
+
+/// The register location for returning the weekday, (0 - 6). Very unreliable, so will calculate
+/// the day of the week instead.
+const REGISTER_WEEKDAY: u8 = 0x06;
+
+/// The register location for returning the day, (0 - 31).
+const REGISTER_DAY: u8 = 0x07;
+
+/// The register location for returning the month, (0 - 11).
+const REGISTER_MONTH: u8 = 0x08;
+
+/// The register location for returning the year, (0 - 99).
+const REGISTER_YEAR: u8 = 0x09;
+
+/// The register location for returning the century.
+const REGISTER_CENTURY: u8 = 0x32;
+
+/// The register location for return the status A register.
+const STATUS_REGISTER_A: u8 = 0x0A;
+
+/// The register location for return the status B register.
+const STATUS_REGISTER_B: u8 = 0x0B;
+
+/// The register location for return the status C register.
+const STATUS_REGISTER_C: u8 = 0x0C;
+
+/// The non-mockable interrupts are on the 8th bit of port 0x70 which is the register select port
+/// for the CMOS. This will need to be disabled when selecting CMOS registers.
+const NMI_BIT: u8 = 0x80;
+
+/// The enum for selecting the status register to read from
+pub const StatusRegister = enum {
+    /// Status register A
+    A,
+
+    /// Status register B
+    B,
+
+    /// Status register C
+    C,
+
+    ///
+    /// Get the register index for the status registers
+    ///
+    /// Arguments:
+    ///     IN reg: StatusRegister - The enum that represents one of the 3 status registers.
+    ///
+    /// Return: u8
+    ///     The register index for one of the 3 status registers.
+    ///
+    pub fn getRegister(reg: StatusRegister) u8 {
+        return switch (reg) {
+            .A => STATUS_REGISTER_A,
+            .B => STATUS_REGISTER_B,
+            .C => STATUS_REGISTER_C,
+        };
+    }
+};
+
+/// The enum for selecting the real time clock registers.
+pub const RtcRegister = enum {
+    /// The seconds register
+    SECOND,
+
+    /// The minutes register
+    MINUTE,
+
+    /// The hours register
+    HOUR,
+
+    /// The days register
+    DAY,
+
+    /// The months register
+    MONTH,
+
+    /// The year register
+    YEAR,
+
+    /// The century register
+    CENTURY,
+
+    ///
+    /// Get the register index for the RTC registers
+    ///
+    /// Arguments:
+    ///     IN reg: RtcRegister - The enum that represents one of the RTC registers.
+    ///
+    /// Return: u8
+    ///     The register index for one of the RTC registers.
+    ///
+    pub fn getRegister(reg: RtcRegister) u8 {
+        return switch (reg) {
+            .SECOND => REGISTER_SECOND,
+            .MINUTE => REGISTER_MINUTE,
+            .HOUR => REGISTER_HOUR,
+            .DAY => REGISTER_DAY,
+            .MONTH => REGISTER_MONTH,
+            .YEAR => REGISTER_YEAR,
+            .CENTURY => REGISTER_CENTURY,
+        };
+    }
+};
+
+///
+/// Tell the CMOS chip to select the given register ready for read or writing to. This also
+/// disables the NMI when disable_nmi is true.
+///
+/// Arguments:
+///     IN reg: u8                    - The register index to select in the CMOS chip.
+///     IN comptime disable_nmi: bool - Whether to disable NMI when selecting a register.
+///
+inline fn selectRegister(reg: u8, comptime disable_nmi: bool) void {
+    if (disable_nmi) {
+        arch.outb(ADDRESS, reg | NMI_BIT);
+    } else {
+        arch.outb(ADDRESS, reg);
+    }
+}
+
+///
+/// Write to the selected register to the CMOS chip.
+///
+/// Arguments:
+///     IN data: u8 - The data to write to the selected register.
+///
+inline fn writeRegister(data: u8) void {
+    arch.outb(DATA, data);
+}
+
+///
+/// Read the selected register from the CMOS chip.
+///
+/// Return: u8
+///     The value in the selected register.
+///
+inline fn readRegister() u8 {
+    return arch.inb(DATA);
+}
+
+///
+/// Select then read a register from the CMOS chip. This include a I/O wait to ensure the CMOS chip
+/// has time to select the register.
+///
+/// Arguments:
+///     IN reg: u8                    - The register index to select in the CMOS chip.
+///     IN comptime disable_nmi: bool - Whether to disable NMI when selecting a register.
+///
+/// Return: u8
+///     The value in the selected register.
+///
+inline fn selectAndReadRegister(reg: u8, comptime disable_nmi: bool) u8 {
+    selectRegister(reg, disable_nmi);
+    arch.ioWait();
+    return readRegister();
+}
+
+///
+/// Select then write to a register to the CMOS chip. This include a I/O wait to ensure the CMOS chip
+/// has time to select the register.
+///
+/// Arguments:
+///     IN reg: u8                    - The register index to select in the CMOS chip.
+///     IN data: u8                   - The data to write to the selected register.
+///     IN comptime disable_nmi: bool - Whether to disable NMI when selecting a register.
+///
+inline fn selectAndWriteRegister(reg: u8, data: u8, comptime disable_nmi: bool) void {
+    selectRegister(reg, disable_nmi);
+    arch.ioWait();
+    writeRegister(data);
+}
+
+///
+/// Read a register that corresponds to a real time clock register.
+///
+/// Arguments:
+///     IN reg: RtcRegister - A RTC register to select in the CMOS chip.
+///
+/// Return: u8
+///     The value in the selected register.
+///
+pub fn readRtcRegister(reg: RtcRegister) u8 {
+    return selectAndReadRegister(reg.getRegister(), false);
+}
+
+///
+/// Read a status register in the CMOS chip.
+///
+/// Arguments:
+///     IN reg: StatusRegister        - The status register to select.
+///     IN comptime disable_nmi: bool - Whether to disable NMI when selecting a register.
+///
+/// Return: u8
+///     The value in the selected register.
+///
+pub fn readStatusRegister(reg: StatusRegister, comptime disable_nmi: bool) u8 {
+    return selectAndReadRegister(reg.getRegister(), disable_nmi);
+}
+
+///
+/// Write to a status register in the CMOS chip.
+///
+/// Arguments:
+///     IN reg: StatusRegister        - The status register to select.
+///     IN data: u8                   - The data to write to the selected register.
+///     IN comptime disable_nmi: bool - Whether to disable NMI when selecting a register.
+///
+pub fn writeStatusRegister(reg: StatusRegister, data: u8, comptime disable_nmi: bool) void {
+    selectAndWriteRegister(reg.getRegister(), data, disable_nmi);
+}
+
+test "selectRegister" {
+    arch.initTest();
+    defer arch.freeTest();
+
+    arch.addTestParams("outb", .{ ADDRESS, STATUS_REGISTER_A });
+
+    const reg = STATUS_REGISTER_A;
+
+    selectRegister(reg, false);
+}
+
+test "selectRegister no NMI" {
+    arch.initTest();
+    defer arch.freeTest();
+
+    arch.addTestParams("outb", .{ ADDRESS, STATUS_REGISTER_A | NMI_BIT });
+
+    const reg = STATUS_REGISTER_A;
+
+    selectRegister(reg, true);
+}
+
+test "writeRegister" {
+    arch.initTest();
+    defer arch.freeTest();
+
+    arch.addTestParams("outb", .{ DATA, @as(u8, 0xAA) });
+
+    const data = @as(u8, 0xAA);
+
+    writeRegister(data);
+}
+
+test "readRegister" {
+    arch.initTest();
+    defer arch.freeTest();
+
+    arch.addTestParams("inb", .{ DATA, @as(u8, 0x55) });
+
+    const expected = @as(u8, 0x55);
+    const actual = readRegister();
+
+    expectEqual(expected, actual);
+}
+
+test "selectAndReadRegister NMI" {
+    arch.initTest();
+    defer arch.freeTest();
+
+    arch.addTestParams("outb", .{ ADDRESS, STATUS_REGISTER_C });
+    arch.addTestParams("inb", .{ DATA, @as(u8, 0x44) });
+    arch.addConsumeFunction("ioWait", arch.mock_ioWait);
+
+    const reg = STATUS_REGISTER_C;
+
+    const expected = @as(u8, 0x44);
+    const actual = selectAndReadRegister(reg, false);
+
+    expectEqual(expected, actual);
+}
+
+test "selectAndReadRegister no NMI" {
+    arch.initTest();
+    defer arch.freeTest();
+
+    arch.addTestParams("outb", .{ ADDRESS, STATUS_REGISTER_C | NMI_BIT });
+    arch.addTestParams("inb", .{ DATA, @as(u8, 0x44) });
+    arch.addConsumeFunction("ioWait", arch.mock_ioWait);
+
+    const reg = STATUS_REGISTER_C;
+
+    const expected = @as(u8, 0x44);
+    const actual = selectAndReadRegister(reg, true);
+
+    expectEqual(expected, actual);
+}
+
+test "selectAndWriteRegister NMI" {
+    arch.initTest();
+    defer arch.freeTest();
+
+    arch.addTestParams("outb", .{ ADDRESS, STATUS_REGISTER_C, DATA, @as(u8, 0x88) });
+    arch.addConsumeFunction("ioWait", arch.mock_ioWait);
+
+    const reg = STATUS_REGISTER_C;
+    const data = @as(u8, 0x88);
+
+    selectAndWriteRegister(reg, data, false);
+}
+
+test "selectAndWriteRegister no NMI" {
+    arch.initTest();
+    defer arch.freeTest();
+
+    arch.addTestParams("outb", .{ ADDRESS, STATUS_REGISTER_C | NMI_BIT, DATA, @as(u8, 0x88) });
+    arch.addConsumeFunction("ioWait", arch.mock_ioWait);
+
+    const reg = STATUS_REGISTER_C;
+    const data = @as(u8, 0x88);
+
+    selectAndWriteRegister(reg, data, true);
+}
+
+test "readRtcRegister" {
+    arch.initTest();
+    defer arch.freeTest();
+
+    arch.addRepeatFunction("ioWait", arch.mock_ioWait);
+
+    const rtc_regs = [_]RtcRegister{ RtcRegister.SECOND, RtcRegister.MINUTE, RtcRegister.HOUR, RtcRegister.DAY, RtcRegister.MONTH, RtcRegister.YEAR, RtcRegister.CENTURY };
+
+    for (rtc_regs) |reg| {
+        const r = switch (reg) {
+            .SECOND => REGISTER_SECOND,
+            .MINUTE => REGISTER_MINUTE,
+            .HOUR => REGISTER_HOUR,
+            .DAY => REGISTER_DAY,
+            .MONTH => REGISTER_MONTH,
+            .YEAR => REGISTER_YEAR,
+            .CENTURY => REGISTER_CENTURY,
+        };
+
+        arch.addTestParams("outb", .{ ADDRESS, r });
+        arch.addTestParams("inb", .{ DATA, @as(u8, 0x44) });
+
+        const expected = @as(u8, 0x44);
+        const actual = readRtcRegister(reg);
+
+        expectEqual(expected, actual);
+    }
+}
+
+test "readStatusRegister NMI" {
+    arch.initTest();
+    defer arch.freeTest();
+
+    arch.addRepeatFunction("ioWait", arch.mock_ioWait);
+
+    const status_regs = [_]StatusRegister{ StatusRegister.A, StatusRegister.B, StatusRegister.C };
+
+    for (status_regs) |reg| {
+        const r = switch (reg) {
+            .A => STATUS_REGISTER_A,
+            .B => STATUS_REGISTER_B,
+            .C => STATUS_REGISTER_C,
+        };
+
+        arch.addTestParams("outb", .{ ADDRESS, r });
+        arch.addTestParams("inb", .{ DATA, @as(u8, 0x78) });
+
+        const expected = @as(u8, 0x78);
+        const actual = readStatusRegister(reg, false);
+
+        expectEqual(expected, actual);
+    }
+}
+
+test "readStatusRegister no NMI" {
+    arch.initTest();
+    defer arch.freeTest();
+
+    arch.addRepeatFunction("ioWait", arch.mock_ioWait);
+
+    const status_regs = [_]StatusRegister{ StatusRegister.A, StatusRegister.B, StatusRegister.C };
+
+    for (status_regs) |reg| {
+        const r = switch (reg) {
+            .A => STATUS_REGISTER_A,
+            .B => STATUS_REGISTER_B,
+            .C => STATUS_REGISTER_C,
+        };
+
+        arch.addTestParams("outb", .{ ADDRESS, r | NMI_BIT });
+        arch.addTestParams("inb", .{ DATA, @as(u8, 0x78) });
+
+        const expected = @as(u8, 0x78);
+        const actual = readStatusRegister(reg, true);
+
+        expectEqual(expected, actual);
+    }
+}
+
+test "writeStatusRegister NMI" {
+    arch.initTest();
+    defer arch.freeTest();
+
+    arch.addRepeatFunction("ioWait", arch.mock_ioWait);
+
+    const status_regs = [_]StatusRegister{ StatusRegister.A, StatusRegister.B, StatusRegister.C };
+
+    for (status_regs) |reg| {
+        const r = switch (reg) {
+            .A => STATUS_REGISTER_A,
+            .B => STATUS_REGISTER_B,
+            .C => STATUS_REGISTER_C,
+        };
+
+        arch.addTestParams("outb", .{ ADDRESS, r, DATA, @as(u8, 0x43) });
+
+        const data = @as(u8, 0x43);
+        writeStatusRegister(reg, data, false);
+    }
+}
+
+test "writeStatusRegister no NMI" {
+    arch.initTest();
+    defer arch.freeTest();
+
+    arch.addRepeatFunction("ioWait", arch.mock_ioWait);
+
+    const status_regs = [_]StatusRegister{ StatusRegister.A, StatusRegister.B, StatusRegister.C };
+
+    for (status_regs) |reg| {
+        const r = switch (reg) {
+            .A => STATUS_REGISTER_A,
+            .B => STATUS_REGISTER_B,
+            .C => STATUS_REGISTER_C,
+        };
+
+        arch.addTestParams("outb", .{ ADDRESS, r | NMI_BIT, DATA, @as(u8, 0x43) });
+
+        const data = @as(u8, 0x43);
+        writeStatusRegister(reg, data, true);
+    }
+}

src/kernel/arch/x86/pic.zig

@@ -436,23 +436,36 @@ pub fn init() void {
 
     // Initiate
     sendCommandMaster(ICW1_INITIALISATION | ICW1_EXPECT_ICW4);
+    arch.ioWait();
     sendCommandSlave(ICW1_INITIALISATION | ICW1_EXPECT_ICW4);
+    arch.ioWait();
 
     // Offsets
     sendDataMaster(ICW2_MASTER_REMAP_OFFSET);
+    arch.ioWait();
     sendDataSlave(ICW2_SLAVE_REMAP_OFFSET);
+    arch.ioWait();
 
     // IRQ lines
     sendDataMaster(ICW3_MASTER_IRQ_MAP_FROM_SLAVE);
+    arch.ioWait();
     sendDataSlave(ICW3_SLAVE_IRQ_MAP_TO_MASTER);
+    arch.ioWait();
 
     // 80x86 mode
     sendDataMaster(ICW4_80x86_MODE);
+    arch.ioWait();
     sendDataSlave(ICW4_80x86_MODE);
+    arch.ioWait();
 
     // Mask all interrupts
     sendDataMaster(0xFF);
+    arch.ioWait();
     sendDataSlave(0xFF);
+    arch.ioWait();
+
+    // Clear the IRQ for the slave
+    clearMask(IRQ_CASCADE_FOR_SLAVE);
 
     log.logInfo("Done\n", .{});
 
@@ -763,6 +776,8 @@ test "init" {
     arch.initTest();
     defer arch.freeTest();
 
+    arch.addRepeatFunction("ioWait", arch.mock_ioWait);
+
     // Just a long list of OUT instructions setting up the PIC
     arch.addTestParams("outb", .{
         MASTER_COMMAND_REG,
@@ -785,8 +800,12 @@ test "init" {
         @as(u8, 0xFF),
         SLAVE_DATA_REG,
         @as(u8, 0xFF),
+        MASTER_DATA_REG,
+        @as(u8, 0xFB),
     });
 
+    arch.addTestParams("inb", .{ MASTER_DATA_REG, @as(u8, 0xFF) });
+
     init();
 }
 
@@ -794,7 +813,8 @@ test "init" {
 /// Test that all the PIC masks are set so no interrupts can fire.
 ///
 fn rt_picAllMasked() void {
-    if (readDataMaster() != 0xFF) {
+    // The master will have interrupt 2 clear because this is the link to the slave (third bit)
+    if (readDataMaster() != 0xFB) {
         panic(@errorReturnTrace(), "Master masks are not set, found: {}\n", .{readDataMaster()});
     }
 

src/kernel/arch/x86/rtc.zig

@@ -0,0 +1,745 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const is_test = builtin.is_test;
+const expect = std.testing.expect;
+const expectEqual = std.testing.expectEqual;
+const expectError = std.testing.expectError;
+const build_options = @import("build_options");
+const mock_path = build_options.arch_mock_path;
+const arch = @import("arch.zig");
+const log = @import("../../log.zig");
+const pic = @import("pic.zig");
+const pit = @import("pit.zig");
+const irq = @import("irq.zig");
+const cmos = if (is_test) @import(mock_path ++ "cmos_mock.zig") else @import("cmos.zig");
+const panic = if (is_test) @import(mock_path ++ "panic_mock.zig").panic else @import("../../panic.zig").panic;
+
+/// The Century register is unreliable. We need a APIC interface to infer if we have a century
+/// register. So this is a current TODO.
+const CURRENT_CENTURY: u32 = 2000;
+
+/// TODO: To do with the unreliable century register. Once have APIC, can use this as a sanity check
+/// if the the century register gives a wild answer then the other RTC values maybe wild. So then
+/// could report that the CMOS chip is faulty or the battery is dyeing.
+const CENTURY_REGISTER: bool = false;
+
+/// A structure to hold all the date and time information in the RTC.
+const DateTime = struct {
+    second: u32,
+    minute: u32,
+    hour: u32,
+    day: u32,
+    month: u32,
+    year: u32,
+    century: u32,
+    day_of_week: u32,
+};
+
+/// The error set that can be returned from some RTC functions.
+const RtcError = error{
+    /// If setting the rate for interrupts is less than 3 or greater than 15.
+    RateError,
+};
+
+/// The number of ticks that has passed when RTC was initially set up.
+var ticks: u32 = 0;
+
+///
+/// Checks if the CMOS chip isn't updating the RTC registers. Call this before reading any RTC
+/// registers so don't get inconsistent values.
+///
+/// Return: bool
+///     Whether the CMOS chip is buzzy and a update is in progress.
+///
+fn isBuzzy() bool {
+    return (cmos.readStatusRegister(cmos.StatusRegister.A, false) & 0x80) != 0;
+}
+
+///
+/// Calculate the day of the week from the given day, month and year.
+///
+/// Arguments:
+///     IN date_time: DateTime - The DateTime structure that holds the current day, month and year.
+///
+/// Return: u8
+///     A number that represents the day of the week. 1 = Sunday, 2 = Monday, ...
+///
+fn calcDayOfWeek(date_time: DateTime) u32 {
+    const t = [_]u8{ 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 };
+    const year = date_time.year - @boolToInt(date_time.month < 3);
+    const month = date_time.month;
+    const day = date_time.day;
+
+    return (year + (year / 4) - (year / 100) + (year / 400) + t[month - 1] + day) % 7;
+}
+
+///
+/// Check if the RTC is in binary coded decimal mode. If the RTC ic counting in BCD, then the 3rd
+/// bit in the status register B will be set.
+///
+/// Return: bool
+///     When the RTC is counting in BCD.
+///
+fn isBcd() bool {
+    const reg_b = cmos.readStatusRegister(cmos.StatusRegister.B, false);
+    return reg_b & 0x04 != 0;
+}
+
+///
+/// Check if the RTC in 12 hour mode. If the RTC is in 12 hour mode, then the 2nd bit in the status
+/// register B is set and the most significant bit on the hour field is set.
+///
+/// Arguments:
+///     IN date_time: DateTime - The DateTime structure containing at least the hour field set.
+///
+/// Return: bool
+///     Whether the RTC is in 12 hour mode.
+///
+fn is12Hr(date_time: DateTime) bool {
+    const reg_b = cmos.readStatusRegister(cmos.StatusRegister.B, false);
+    return reg_b & 0x02 != 0 and date_time.hour & 0x80 != 0;
+}
+
+///
+/// Convert BCD to binary.
+///
+/// Arguments:
+///     IN bcd: u32 - The binary coded decimal value to convert
+///
+/// Return: u32
+///     The converted BCD value.
+///
+fn bcdToBinary(bcd: u32) u32 {
+    return ((bcd & 0xF0) >> 1) + ((bcd & 0xF0) >> 3) + (bcd & 0xf);
+}
+
+///
+/// Read the real time clock registers and return them in the DateTime structure. This will read
+/// the seconds, minutes, hours, days, months, years, century and day of the week.
+///
+/// Return: DateTime
+///     The data from the CMOS RTC registers.
+///
+fn readRtcRegisters() DateTime {
+    // Make sure there isn't a update in progress
+    while (isBuzzy()) {}
+
+    var date_time = DateTime{
+        .second = cmos.readRtcRegister(cmos.RtcRegister.SECOND),
+        .minute = cmos.readRtcRegister(cmos.RtcRegister.MINUTE),
+        .hour = cmos.readRtcRegister(cmos.RtcRegister.HOUR),
+        .day = cmos.readRtcRegister(cmos.RtcRegister.DAY),
+        .month = cmos.readRtcRegister(cmos.RtcRegister.MONTH),
+        .year = cmos.readRtcRegister(cmos.RtcRegister.YEAR),
+        .century = if (CENTURY_REGISTER) cmos.readRtcRegister(cmos.RtcRegister.CENTURY) else CURRENT_CENTURY,
+        // This will be filled in later
+        .day_of_week = 0,
+    };
+
+    // The day of the week register is also very unreliable, so is better to calculate it
+    date_time.day_of_week = calcDayOfWeek(date_time);
+
+    return date_time;
+}
+
+///
+/// Read a stable time from the real time clock registers on the CMOS chip and return a BCD and
+/// 12 hour converted date and time.
+///
+/// Return: DateTime
+///     The data from the CMOS RTC registers with correct BCD conversions, 12 hour conversions and
+///     the century added to the year.
+///
+fn readRtc() DateTime {
+    var date_time1 = readRtcRegisters();
+    var date_time2 = readRtcRegisters();
+
+    // Use the method: Read the registers twice and check if they are the same so to avoid
+    // inconsistent values due to RTC updates
+
+    var compare = false;
+
+    inline for (@typeInfo(DateTime).Struct.fields) |field| {
+        compare = compare or @field(date_time1, field.name) != @field(date_time2, field.name);
+    }
+
+    while (compare) {
+        date_time1 = readRtcRegisters();
+        date_time2 = readRtcRegisters();
+
+        compare = false;
+        inline for (@typeInfo(DateTime).Struct.fields) |field| {
+            compare = compare or @field(date_time1, field.name) != @field(date_time2, field.name);
+        }
+    }
+
+    // Convert BCD to binary if necessary
+    if (isBcd()) {
+        date_time1.second = bcdToBinary(date_time1.second);
+        date_time1.minute = bcdToBinary(date_time1.minute);
+        // Needs a special calculation because the upper bit is set
+        date_time1.hour = ((date_time1.hour & 0x0F) + (((date_time1.hour & 0x70) / 16) * 10)) | (date_time1.hour & 0x80);
+        date_time1.day = bcdToBinary(date_time1.day);
+        date_time1.month = bcdToBinary(date_time1.month);
+        date_time1.year = bcdToBinary(date_time1.year);
+        if (CENTURY_REGISTER) {
+            date_time1.century = bcdToBinary(date_time1.century);
+        }
+    }
+
+    // Need to add on the century to the year
+    if (CENTURY_REGISTER) {
+        date_time1.year += date_time1.century * 100;
+    } else {
+        date_time1.year += CURRENT_CENTURY;
+    }
+
+    // Convert to 24hr time
+    if (is12Hr(date_time1)) {
+        date_time1.hour = ((date_time1.hour & 0x7F) + 12) % 24;
+    }
+
+    return date_time1;
+}
+
+///
+/// The interrupt handler for the RTC.
+///
+/// Arguments:
+///     IN ctx: *arch.InterruptContext - Pointer to the interrupt context containing the contents
+///                                      of the register at the time of the interrupt.
+///
+fn rtcHandler(ctx: *arch.InterruptContext) void {
+    ticks +%= 1;
+
+    // Need to read status register C
+    const reg_c = cmos.readStatusRegister(cmos.StatusRegister.C, false);
+}
+
+///
+/// Set the rate at which the interrupts will fire. Ranges from 0x3 to 0xF. Where the frequency
+/// is determined by: frequency = 32768 >> (rate-1); This will assume the interrupts are disabled.
+///
+/// Arguments:
+///     IN rate: u4 - The rate value to set the frequency to.
+///
+/// Error: RtcError
+///     RtcError.RateError - If the rate is less than 3.
+///
+fn setRate(rate: u8) RtcError!void {
+    if (rate < 3 or rate > 0xF) {
+        return RtcError.RateError;
+    }
+
+    // Need to disable the NMI for this process
+    const status_a = cmos.readStatusRegister(cmos.StatusRegister.A, true);
+    cmos.writeStatusRegister(cmos.StatusRegister.A, (status_a & 0xF0) | rate, true);
+}
+
+///
+/// Enable interrupts for the RTC. This will assume the interrupts have been disabled before hand.
+///
+fn enableInterrupts() void {
+    // Need to disable the NMI for this process
+    const status_b = cmos.readStatusRegister(cmos.StatusRegister.B, true);
+
+    // Set the 7th bit to enable interrupt
+    cmos.writeStatusRegister(cmos.StatusRegister.B, status_b | 0x40, true);
+}
+
+///
+/// Initialise the RTC.
+///
+pub fn init() void {
+    log.logInfo("Init rtc\n", .{});
+
+    // Register the interrupt handler
+    irq.registerIrq(pic.IRQ_REAL_TIME_CLOCK, rtcHandler) catch |err| switch (err) {
+        error.IrqExists => {
+            panic(@errorReturnTrace(), "IRQ for RTC, IRQ number: {} exists", .{pic.IRQ_REAL_TIME_CLOCK});
+        },
+        error.InvalidIrq => {
+            panic(@errorReturnTrace(), "IRQ for RTC, IRQ number: {} is invalid", .{pic.IRQ_REAL_TIME_CLOCK});
+        },
+    };
+
+    // Need to disable interrupts went setting up the RTC
+    arch.disableInterrupts();
+
+    // Set the interrupt rate to 512Hz
+    setRate(7) catch |err| switch (err) {
+        error.RateError => {
+            panic(@errorReturnTrace(), "Setting rate error", .{});
+        },
+    };
+
+    // Enable RTC interrupts
+    enableInterrupts();
+
+    // Read status register C to clear any interrupts that may have happened during set up
+    //const reg_c = cmos.readStatusRegister(cmos.StatusRegister.C, false);
+
+    // Can now enable interrupts
+    arch.enableInterrupts();
+
+    const reg_c = cmos.readStatusRegister(cmos.StatusRegister.C, false);
+
+    log.logInfo("Done\n", .{});
+
+    if (build_options.rt_test) runtimeTests();
+}
+
+test "isBuzzy not buzzy" {
+    cmos.initTest();
+    defer cmos.freeTest();
+
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.A, false, @as(u8, 0x60) },
+    );
+
+    expect(!isBuzzy());
+}
+
+test "isBuzzy buzzy" {
+    cmos.initTest();
+    defer cmos.freeTest();
+
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.A, false, @as(u8, 0x80) },
+    );
+
+    expect(isBuzzy());
+}
+
+test "calcDayOfWeek" {
+    var date_time = DateTime{
+        .second = 0,
+        .minute = 0,
+        .hour = 0,
+        .day = 10,
+        .month = 1,
+        .year = 2020,
+        .century = 0,
+        .day_of_week = 0,
+    };
+
+    var actual = calcDayOfWeek(date_time);
+    var expected = @as(u32, 5);
+
+    expectEqual(expected, actual);
+
+    date_time.day = 20;
+    date_time.month = 7;
+    date_time.year = 1940;
+
+    actual = calcDayOfWeek(date_time);
+    expected = @as(u32, 6);
+
+    expectEqual(expected, actual);
+
+    date_time.day = 9;
+    date_time.month = 11;
+    date_time.year = 2043;
+
+    actual = calcDayOfWeek(date_time);
+    expected = @as(u32, 1);
+
+    expectEqual(expected, actual);
+
+    date_time.day = 1;
+    date_time.month = 1;
+    date_time.year = 2000;
+
+    actual = calcDayOfWeek(date_time);
+    expected = @as(u32, 6);
+
+    expectEqual(expected, actual);
+}
+
+test "isBcd not BCD" {
+    cmos.initTest();
+    defer cmos.freeTest();
+
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.B, false, @as(u8, 0x00) },
+    );
+
+    expect(!isBcd());
+}
+
+test "isBcd BCD" {
+    cmos.initTest();
+    defer cmos.freeTest();
+
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.B, false, @as(u8, 0x04) },
+    );
+
+    expect(isBcd());
+}
+
+test "is12Hr not 12Hr" {
+    const date_time = DateTime{
+        .second = 0,
+        .minute = 0,
+        .hour = 0,
+        .day = 0,
+        .month = 0,
+        .year = 0,
+        .century = 0,
+        .day_of_week = 0,
+    };
+
+    cmos.initTest();
+    defer cmos.freeTest();
+
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.B, false, @as(u8, 0x00) },
+    );
+
+    expect(!is12Hr(date_time));
+}
+
+test "is12Hr 12Hr" {
+    const date_time = DateTime{
+        .second = 0,
+        .minute = 0,
+        .hour = 0x80,
+        .day = 0,
+        .month = 0,
+        .year = 0,
+        .century = 0,
+        .day_of_week = 0,
+    };
+
+    cmos.initTest();
+    defer cmos.freeTest();
+
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.B, false, @as(u8, 0x02) },
+    );
+
+    expect(is12Hr(date_time));
+}
+
+test "bcdToBinary" {
+    var expected = @as(u32, 59);
+    var actual = bcdToBinary(0x59);
+
+    expectEqual(expected, actual);
+
+    expected = @as(u32, 48);
+    actual = bcdToBinary(0x48);
+
+    expectEqual(expected, actual);
+
+    expected = @as(u32, 1);
+    actual = bcdToBinary(0x01);
+
+    expectEqual(expected, actual);
+}
+
+test "readRtcRegisters" {
+    cmos.initTest();
+    defer cmos.freeTest();
+
+    // Have 2 buzzy loops
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.A, false, @as(u8, 0x80), cmos.StatusRegister.A, false, @as(u8, 0x80), cmos.StatusRegister.A, false, @as(u8, 0x00) },
+    );
+
+    // All the RTC registers without century as it isn't supported yet
+    cmos.addTestParams("readRtcRegister", .{
+        cmos.RtcRegister.SECOND, @as(u8, 1),
+        cmos.RtcRegister.MINUTE, @as(u8, 2),
+        cmos.RtcRegister.HOUR,   @as(u8, 3),
+        cmos.RtcRegister.DAY,    @as(u8, 10),
+        cmos.RtcRegister.MONTH,  @as(u8, 1),
+        cmos.RtcRegister.YEAR,   @as(u8, 20),
+    });
+
+    const expected = DateTime{
+        .second = 1,
+        .minute = 2,
+        .hour = 3,
+        .day = 10,
+        .month = 1,
+        .year = 20,
+        .century = 2000,
+        .day_of_week = 5,
+    };
+    const actual = readRtcRegisters();
+
+    expectEqual(expected, actual);
+}
+
+test "readRtc unstable read" {
+    cmos.initTest();
+    defer cmos.freeTest();
+
+    // No buzzy loop
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.A, false, @as(u8, 0x00), cmos.StatusRegister.A, false, @as(u8, 0x00) },
+    );
+
+    // Reading the RTC registers twice, second time is one second ahead
+    cmos.addTestParams("readRtcRegister", .{
+        cmos.RtcRegister.SECOND, @as(u8, 1),
+        cmos.RtcRegister.MINUTE, @as(u8, 2),
+        cmos.RtcRegister.HOUR,   @as(u8, 3),
+        cmos.RtcRegister.DAY,    @as(u8, 10),
+        cmos.RtcRegister.MONTH,  @as(u8, 1),
+        cmos.RtcRegister.YEAR,   @as(u8, 20),
+        cmos.RtcRegister.SECOND, @as(u8, 2),
+        cmos.RtcRegister.MINUTE, @as(u8, 2),
+        cmos.RtcRegister.HOUR,   @as(u8, 3),
+        cmos.RtcRegister.DAY,    @as(u8, 10),
+        cmos.RtcRegister.MONTH,  @as(u8, 1),
+        cmos.RtcRegister.YEAR,   @as(u8, 20),
+    });
+
+    // Will try again, and now stable
+    // No buzzy loop
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.A, false, @as(u8, 0x00), cmos.StatusRegister.A, false, @as(u8, 0x00) },
+    );
+    cmos.addTestParams("readRtcRegister", .{
+        cmos.RtcRegister.SECOND, @as(u8, 2),
+        cmos.RtcRegister.MINUTE, @as(u8, 2),
+        cmos.RtcRegister.HOUR,   @as(u8, 3),
+        cmos.RtcRegister.DAY,    @as(u8, 10),
+        cmos.RtcRegister.MONTH,  @as(u8, 1),
+        cmos.RtcRegister.YEAR,   @as(u8, 20),
+        cmos.RtcRegister.SECOND, @as(u8, 2),
+        cmos.RtcRegister.MINUTE, @as(u8, 2),
+        cmos.RtcRegister.HOUR,   @as(u8, 3),
+        cmos.RtcRegister.DAY,    @as(u8, 10),
+        cmos.RtcRegister.MONTH,  @as(u8, 1),
+        cmos.RtcRegister.YEAR,   @as(u8, 20),
+    });
+
+    // Not BCD
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.B, false, @as(u8, 0x00) },
+    );
+
+    // Not 12hr
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.B, false, @as(u8, 0x00) },
+    );
+
+    const expected = DateTime{
+        .second = 2,
+        .minute = 2,
+        .hour = 3,
+        .day = 10,
+        .month = 1,
+        .year = 2020,
+        .century = 2000,
+        .day_of_week = 5,
+    };
+    const actual = readRtc();
+
+    expectEqual(expected, actual);
+}
+
+test "readRtc is BCD" {
+    cmos.initTest();
+    defer cmos.freeTest();
+
+    // No buzzy loop
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.A, false, @as(u8, 0x00), cmos.StatusRegister.A, false, @as(u8, 0x00) },
+    );
+
+    // Reading the RTC registers once
+    cmos.addTestParams("readRtcRegister", .{
+        cmos.RtcRegister.SECOND, @as(u8, 0x30),
+        cmos.RtcRegister.MINUTE, @as(u8, 0x59),
+        cmos.RtcRegister.HOUR,   @as(u8, 0x11),
+        cmos.RtcRegister.DAY,    @as(u8, 0x10),
+        cmos.RtcRegister.MONTH,  @as(u8, 0x1),
+        cmos.RtcRegister.YEAR,   @as(u8, 0x20),
+        cmos.RtcRegister.SECOND, @as(u8, 0x30),
+        cmos.RtcRegister.MINUTE, @as(u8, 0x59),
+        cmos.RtcRegister.HOUR,   @as(u8, 0x11),
+        cmos.RtcRegister.DAY,    @as(u8, 0x10),
+        cmos.RtcRegister.MONTH,  @as(u8, 0x1),
+        cmos.RtcRegister.YEAR,   @as(u8, 0x20),
+    });
+
+    // BCD
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.B, false, @as(u8, 0x04) },
+    );
+
+    // Not 12hr
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.B, false, @as(u8, 0x00) },
+    );
+
+    const expected = DateTime{
+        .second = 30,
+        .minute = 59,
+        .hour = 11,
+        .day = 10,
+        .month = 1,
+        .year = 2020,
+        .century = 2000,
+        .day_of_week = 5,
+    };
+    const actual = readRtc();
+
+    expectEqual(expected, actual);
+}
+
+test "readRtc is 12 hours" {
+    cmos.initTest();
+    defer cmos.freeTest();
+
+    // No buzzy loop
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.A, false, @as(u8, 0x00), cmos.StatusRegister.A, false, @as(u8, 0x00) },
+    );
+
+    // Reading the RTC registers once
+    cmos.addTestParams("readRtcRegister", .{
+        cmos.RtcRegister.SECOND, @as(u8, 1),
+        cmos.RtcRegister.MINUTE, @as(u8, 2),
+        cmos.RtcRegister.HOUR,   @as(u8, 0x83),
+        cmos.RtcRegister.DAY,    @as(u8, 10),
+        cmos.RtcRegister.MONTH,  @as(u8, 1),
+        cmos.RtcRegister.YEAR,   @as(u8, 20),
+        cmos.RtcRegister.SECOND, @as(u8, 1),
+        cmos.RtcRegister.MINUTE, @as(u8, 2),
+        cmos.RtcRegister.HOUR,   @as(u8, 0x83),
+        cmos.RtcRegister.DAY,    @as(u8, 10),
+        cmos.RtcRegister.MONTH,  @as(u8, 1),
+        cmos.RtcRegister.YEAR,   @as(u8, 20),
+    });
+
+    // Not BCD
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.B, false, @as(u8, 0x00) },
+    );
+
+    // 12hr
+    cmos.addTestParams(
+        "readStatusRegister",
+        .{ cmos.StatusRegister.B, false, @as(u8, 0x02) },
+    );
+
+    const expected = DateTime{
+        .second = 1,
+        .minute = 2,
+        .hour = 15,
+        .day = 10,
+        .month = 1,
+        .year = 2020,
+        .century = 2000,
+        .day_of_week = 5,
+    };
+    const actual = readRtc();
+
+    expectEqual(expected, actual);
+}
+
+test "setRate below 3" {
+    expectError(RtcError.RateError, setRate(0));
+    expectError(RtcError.RateError, setRate(1));
+    expectError(RtcError.RateError, setRate(2));
+}
+
+test "setRate" {
+    cmos.initTest();
+    defer cmos.freeTest();
+
+    cmos.addTestParams("readStatusRegister", .{ cmos.StatusRegister.A, true, @as(u8, 0x10) });
+    cmos.addTestParams("writeStatusRegister", .{ cmos.StatusRegister.A, @as(u8, 0x17), true });
+
+    const rate = @as(u8, 7);
+    try setRate(rate);
+}
+
+test "enableInterrupts" {
+    cmos.initTest();
+    defer cmos.freeTest();
+
+    cmos.addTestParams("readStatusRegister", .{ cmos.StatusRegister.B, true, @as(u8, 0x20) });
+    cmos.addTestParams("writeStatusRegister", .{ cmos.StatusRegister.B, @as(u8, 0x60), true });
+
+    enableInterrupts();
+}
+
+///
+/// Check that the IRQ is registered correctly
+///
+fn rt_init() void {
+    var irq_exists = false;
+    irq.registerIrq(pic.IRQ_REAL_TIME_CLOCK, rtcHandler) catch |err| switch (err) {
+        error.IrqExists => {
+            // We should get this error
+            irq_exists = true;
+        },
+        error.InvalidIrq => {
+            panic(@errorReturnTrace(), "IRQ for RTC, IRQ number: {} is invalid", .{pic.IRQ_REAL_TIME_CLOCK});
+        },
+    };
+
+    if (!irq_exists) {
+        panic(@errorReturnTrace(), "IRQ for RTC doesn't exists\n", .{});
+    }
+
+    // Check the rate
+    const status_a = cmos.readStatusRegister(cmos.StatusRegister.A, false);
+    if (status_a & @as(u8, 0x0F) != 7) {
+        panic(@errorReturnTrace(), "Rate not set properly, got: {}\n", .{status_a & @as(u8, 0x0F)});
+    }
+
+    // Check if interrupts are enabled
+    const status_b = cmos.readStatusRegister(cmos.StatusRegister.B, true);
+    if (status_b & ~@as(u8, 0x40) == 0) {
+        panic(@errorReturnTrace(), "Interrupts not enabled\n", .{});
+    }
+
+    log.logInfo("RTC: Tested init\n", .{});
+}
+
+///
+/// Check if the interrupt handler is called after a sleep so check that the RTC interrupts fire.
+///
+fn rt_interrupts() void {
+    const prev_ticks = ticks;
+
+    pit.waitTicks(100);
+
+    if (prev_ticks == ticks) {
+        panic(@errorReturnTrace(), "No interrupt happened\n", .{});
+    }
+
+    log.logInfo("RTC: Tested interrupts\n", .{});
+}
+
+///
+/// Run all the runtime tests.
+///
+fn runtimeTests() void {
+    rt_init();
+    rt_interrupts();
+}