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Length: 1900 (0x76c)
Types: TextFile
Notes: UNIX file
Names: »timer.h«
└─⟦26887b7e0⟧ Bits:30009717 Comet 32 harddisk image
└─⟦28c352965⟧ »/a« UNIX Filesystem
└─⟦this⟧ »usr/include/sys/timer.h«
/*
* @(#)timer.h 3.3 7/14/83
* @(#)Copyright (C) 1983 by National Semiconductor Corp.
*/
/*************************************************************************
** **
** The 8253 programmable interval timer **
** **
** Timers 0 & 1 are dedicated to the 8251 as the receive & xmit **
** baud clocks. Timer 2 is used as the system time clock. **
**************************************************************************/
struct n8253 { /* National 8253 device */
u_short rxclk; /* clock 0 is receiver clock */
u_short txclk; /* clock 1 is xmitter clock */
u_short clock; /* clock 2 is system clock */
u_short mode; /* timer mode register */
};
#define TIMER struct n8253
/* Definition of mode control bits */
/* Counter selection */
#define SC0 0x00 /* Select counter 0 */
#define SC1 0x40 /* Select counter 1 */
#define SC2 0x80 /* Select counter 2 */
/* Read/Load bits */
#define LATCH 0x00 /* Latch counter */
#define HIBYTE 0x20 /* Read/Load counter hi byte */
#define LOBYTE 0x10 /* Read/Load counter lo byte */
#define BYTES2 0x30 /* Read/Load both counter bytes */
/* Mode control bits */
#define TIM_MODE0 0x00 /* Interrupt on terminal count */
#define TIM_MODE1 0x02 /* Programmable one-shot */
#define TIM_MODE2 0x04 /* Rate generator */
#define TIM_MODE3 0x06 /* Square wave rate generator */
#define TIM_MODE4 0x08 /* Software triggered strobe */
#define TIM_MODE5 0x0a /* Hardware triggered strobe */
/* BCD counter */
#define BCDCOUNT 0x01 /* Count value is BCD */
/*
** Counter 2 definitions for system time clock. **
** **
** Input for the 8253 will be 1.8432MHZ. This will require a **
** value of 30720 to give a 60 HZ clock **/
#define C2MODE SC2+BYTES2+TIM_MODE2
#define C2VAL 30720
#ifndef BYTE
#define BYTE *(char *)& /* Causes compiler to generate byte movs */
#endif