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