190 lines
7.1 KiB
C#
190 lines
7.1 KiB
C#
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///////////////////////////////////////////////////////////////////////////////
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//
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// Microsoft Research Singularity
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//
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// Copyright (c) Microsoft Corporation. All rights reserved.
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//
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// File: Timer8254.cs
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//
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// Useful reference URLs:
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// http://developer.intel.com/design/archives/periphrl/index.htm
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// http://developer.intel.com/design/archives/periphrl/docs/7203.htm
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// http://developer.intel.com/design/archives/periphrl/docs/23124406.htm
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//
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using Microsoft.Singularity.Io;
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using Microsoft.Singularity.Configuration;
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using System;
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using System.Threading;
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using System.Diagnostics;
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namespace Microsoft.Singularity.Hal
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{
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[DriverCategory]
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[Signature("/pnp/PNP0100")]
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public sealed class Timer8254Resources : DriverCategoryDeclaration
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{
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[IoPortRange(0, Default = 0x0040, Length = 0x04)]
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public IoPortRange port1;
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[IoIrqRange(1, Default = 0x00, Length = 0x01)]
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public IoIrqRange irq1;
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[IoFixedPortRange(Base = 0x0061, Length = 0x01)]
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public IoPortRange port2;
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}
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/*
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* Note on the i8254 timer:
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*
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* The clock is driven by a 14.318 MHz clock through a divide-by-12
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* counter.
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* This gives a clock frequency of 1.193 MHz.
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* Each tick is therefore 0.838 microseconds long.
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* Thus a 16 bit timer gives us a maximum delay of 0.05 seconds.
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*/
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[CLSCompliant(false)]
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public sealed class Timer8254
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{
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/* Registers */
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const byte i8254_C2 = 0x02; /* counter 2 */
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const byte i8254_CW = 0x03; /* control word */
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/*
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The control word to the 8254 is composed of four fields:
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bits 6-7: select the counter
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bits 4-5: select read/write
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bits 1-3: mode to use
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bit 0 : BCD mode
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*/
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/* bits 6-7 select the counter */
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const byte i8254_CW_SEL0 = 0x00; /* select counter 0 */
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const byte i8254_CW_SEL1 = 0x40; /* select counter 1 */
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const byte i8254_CW_SEL2 = 0x80; /* select counter 2 */
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const byte i8254_CW_RBC = 0xc0; /* read-back command */
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/* bits 4-5 select transaction type */
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const byte i8254_CW_CLC = 0x00; /* counter latch comm. */
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const byte i8254_CW_LSB = 0x10; /* r/w lsb only */
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const byte i8254_CW_MSB = 0x20; /* r/w msb only */
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const byte i8254_CW_BOTH = 0x30; /* r/w lsb, then msb */
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/* bits 1-3 select the mode. bit 3 is sometimes a don't care */
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const byte i8254_CW_MODE0 = 0x00; /* int. on term. count */
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const byte i8254_CW_MODE1 = 0x02; /* h/w retrig. one-shot */
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const byte i8254_CW_MODE2 = 0x04; /* rate generator */
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const byte i8254_CW_MODE3 = 0x06; /* square wave mode */
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const byte i8254_CW_MODE4 = 0x08; /* s/w trig. strobe */
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const byte i8254_CW_MODE5 = 0x0a; /* h/w trig. strobe */
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/* bit 0 sets BCD mode, if you really must */
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const byte i8254_CW_BCD = 0x01; /* set BCD operation */
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/* read-back commands use bits 4 and 5 to return status these
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* are the wrong way round since the bits are inverted (RTFDS).
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*/
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const byte i8254_RB_NOSTATUS = 0xd0; /* Don't get latched count */
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const byte i8254_RB_NOCOUNT = 0xe0; /* Don't get status */
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const byte i8254_RB_ALL = 0xc0; /* Get status and count */
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/* read-back commands use bits 3-1 to select counter */
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const byte i8254_RB_SEL2 = 0x08; /* counter 2 */
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/* status from read-back is returned in bits 6-7 */
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const byte i8254_RB_OUT = 0x80; /* out pin value */
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const byte i8254_RB_NULL = 0x40; /* 1 = count null */
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private static readonly int DefaultTicksPerSecond = 1193182;
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private static readonly int SystemTicksPerSecond = 10000000;
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private PnpConfig config;
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private byte irq;
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private int frequency = DefaultTicksPerSecond;
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/* IOPorts */
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private IoPort C2Port;
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private IoPort CWPort;
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// Constructor
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internal Timer8254(PnpConfig config)
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{
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// /pnp/08/02/01/PNP0100 0003 cfg dis : ISA 8254 Timer : AT Timer
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// IRQ mask=0001 type=47
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// I/O Port inf=01 min=0040 max=0040 aln=01 len=04 0040..0043
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this.config = config;
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this.irq = ((IoIrqRange)config.DynamicRanges[1]).Irq;
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IoPortRange ioPorts = (IoPortRange) config.DynamicRanges[0];
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C2Port = ioPorts.PortAtOffset(i8254_C2, 1, Access.ReadWrite);
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CWPort = ioPorts.PortAtOffset(i8254_CW, 1, Access.ReadWrite);
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// Use Timer2 as it's not connected as interrupt source.
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//
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// Lower 2 bits of port 61 are described in:
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// The Indispensable PC Hardware Book (3rd Edition) p.724
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ioPorts = (IoPortRange) config.FixedRanges[0];
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IoPort p = ioPorts.PortAtOffset(0, 1, Access.ReadWrite);
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p.Write8((byte) ((p.Read8() & 0xfc) | 0x01));
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}
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internal void Start(ushort pitTicks)
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{
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CWPort.Write8(i8254_CW_MODE2 | i8254_CW_BOTH | i8254_CW_SEL2);
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C2Port.Write8((byte)(pitTicks & 0xff));
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C2Port.Write8((byte)(pitTicks >> 8));
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do {
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CWPort.Write8(i8254_RB_NOCOUNT | i8254_RB_SEL2);
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} while ((C2Port.Read8() & i8254_RB_NULL) == i8254_RB_NULL);
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}
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internal ushort Read()
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{
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CWPort.Write8(i8254_RB_NOSTATUS | i8254_RB_SEL2);
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return (ushort)(C2Port.Read8() | (C2Port.Read8() << 8));
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}
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internal void Stop()
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{
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CWPort.Write8(i8254_CW_MODE2 | i8254_CW_BOTH | i8254_CW_SEL2);
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C2Port.Write8((byte)(0)); /* LSB */
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/* C2Port.Write8((byte)(0)); MSB DON'T! */
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}
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internal void SetFrequency(uint newFrequency)
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{
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frequency = (int)newFrequency;
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DebugStub.Print("i8254 frequency {0} Hz\n", __arglist(frequency));
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}
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internal uint TimeSpanToTimerTicks(uint ts)
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{
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return (uint) ((ulong)ts * (uint)(frequency / SystemTicksPerSecond));
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}
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internal uint TimerToTimeSpanTicks(uint ts)
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{
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return (uint) ((ulong)ts * (uint)(SystemTicksPerSecond / frequency));
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}
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#if FIXED_FREQUENCY
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internal static int TimeSpanTicksToPitTicks(int ts)
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{
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// t = 1193182 * T / (10^7) = 0.1193182 * T
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// = T * (1/0x10 + 0xe8ba/0x100000)
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int tmp = (ts * 0xe8ba) >> 20;
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return tmp + (ts >> 4);
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}
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internal static int PitTicksToTimeSpanTicks(int delta)
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{
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// T = 10^7 * t / 1193182 = 8.3809511 * t
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// = t * (8 + 0x6186/0x10000)
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return (delta << 3) + ((delta * 0x6186) >> 16);
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}
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#endif
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}
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}
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