55 lines
2.1 KiB
C
55 lines
2.1 KiB
C
/*
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* libcaca Colour ASCII-Art library
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* Copyright (c) 2006 Sam Hocevar <sam@hocevar.net>
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* 2009 Jean-Yves Lamoureux <jylam@lnxscene.org>
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* All Rights Reserved
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*
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* This library is free software. It comes without any warranty, to
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* the extent permitted by applicable law. You can redistribute it
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* and/or modify it under the terms of the Do What the Fuck You Want
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* to Public License, Version 2, as published by Sam Hocevar. See
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* http://www.wtfpl.net/ for more details.
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*/
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#include "kernel.h"
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#include "klibc.h"
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#include "timer.h"
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u32 ticks = 0;
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void timer_phase(int hz)
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{
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unsigned int divisor = 1193180 / hz; /* Calculate our divisor */
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/*
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0x43 is the Mode/Command register
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From http://wiki.osdev.org/Programmable_Interval_Timer#Read_Back_Status_Byte :
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Bits Usage
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6 and 7 Select channel :
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0 0 = Channel 0
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0 1 = Channel 1
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1 0 = Channel 2
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1 1 = Read-back command (8254 only)
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4 and 5 Access mode :
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0 0 = Latch count value command
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0 1 = Access mode: lobyte only
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1 0 = Access mode: hibyte only
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1 1 = Access mode: lobyte/hibyte
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1 to 3 Operating mode :
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0 0 0 = Mode 0 (interrupt on terminal count)
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0 0 1 = Mode 1 (hardware re-triggerable one-shot)
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0 1 0 = Mode 2 (rate generator)
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0 1 1 = Mode 3 (square wave generator)
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1 0 0 = Mode 4 (software triggered strobe)
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1 0 1 = Mode 5 (hardware triggered strobe)
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1 1 0 = Mode 2 (rate generator, same as 010b)
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1 1 1 = Mode 3 (square wave generator, same as 011b)
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0 BCD/Binary mode: 0 = 16-bit binary, 1 = four-digit BCD
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*/
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unsigned short command = 0b00110110;
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outb(0x43, command);
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outb(0x40, divisor & 0xFF); /* Set low byte of divisor */
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outb(0x40, divisor >> 8); /* Set high byte of divisor */
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}
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