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/* Defines for routines to implement a low-overhead timer for drivers */ 
 
 /* 
 * This program is free software; you can redistribute it and/or 
 * modify it under the terms of the GNU General Public License as 
 * published by the Free Software Foundation; either version 2, or (at 
 * your option) any later version. 
 */ 
 
#ifndef	TIMER_H 
#define TIMER_H 
 
/* Ports for the 8254 timer chip */ 
#define	TIMER2_PORT	0x42 
#define	TIMER_MODE_PORT	0x43 
 
/* Meaning of the mode bits */ 
#define	TIMER0_SEL	0x00 
#define	TIMER1_SEL	0x40 
#define	TIMER2_SEL	0x80 
#define	READBACK_SEL	0xC0 
 
#define	LATCH_COUNT	0x00 
#define	LOBYTE_ACCESS	0x10 
#define	HIBYTE_ACCESS	0x20 
#define	WORD_ACCESS	0x30 
 
#define	MODE0		0x00 
#define	MODE1		0x02 
#define	MODE2		0x04 
#define	MODE3		0x06 
#define	MODE4		0x08 
#define	MODE5		0x0A 
 
#define	BINARY_COUNT	0x00 
#define	BCD_COUNT	0x01 
 
/* Timers tick over at this rate */ 
#define	TICKS_PER_MS	1193 
 
/* Parallel Peripheral Controller Port B */ 
#define	PPC_PORTB	0x61 
 
/* Meaning of the port bits */ 
#define	PPCB_T2OUT	0x20	/* Bit 5 */ 
#define	PPCB_SPKR	0x02	/* Bit 1 */ 
#define	PPCB_T2GATE	0x01	/* Bit 0 */ 
 
/* Ticks must be between 0 and 65535 (0 == 65536) 
   because it is a 16 bit counter */ 
extern void load_timer2(unsigned int ticks); 
extern int timer2_running(void); 
 
extern void waiton_timer2(unsigned int ticks); 
 
#endif	/* TIMER_H */