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Clean up and comment a bit.

This commit is contained in:
briggs 1996-02-01 03:40:26 +00:00
parent dc8adb9e7c
commit af9bcab2ce
1 changed files with 15 additions and 10 deletions
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25
sys/arch/mac68k/mac68k/clockreg.h
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@ -1,4 +1,4 @@
/* $NetBSD: clockreg.h,v 1.3 1994/10/26 08:46:56 cgd Exp $ */
/* $NetBSD: clockreg.h,v 1.4 1996/02/01 03:40:26 briggs Exp $ */
/*-
* Copyright (C) 1993 Allen K. Briggs, Chris P. Caputo,
@ -34,18 +34,23 @@
*
*/
/*
Clock defines and things.
MacII clock characteristics used.
*/
#include "../include/limits.h" /* to get CLK_TCK */
* Clock defines and things.
* MacII clock characteristics used.
*/
#define CLK_SPEED 0.0000012766 /* time to complete a clock (3 MHz) */
#define CLK_INTERVAL 13055 /* clocks to hit CLK_TCK ticks per sec */
/* 7526 for 120 Hz. */
/* 13055 for 60 Hz. */
#define CLK_INTERVAL 13055 /* clks to hit HZ ticks/sec */
/*
* The VIA1 clock speed is 1.2766us, so the timer value above is:
*
* 1 1,000,000us 1
* CLK_INTERVAL = -------- * ----------- * ------
* 1.2766us 1s HZ
*
* where HZ == 60. This gives us 13055.5 and change... We round down.
*/
#define CLK_INTH (CLK_INTERVAL >> 8)
#define CLK_INTL (CLK_INTERVAL & 0xff)