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      1 /*	$NetBSD: clockreg.h,v 1.9 2006/11/20 20:48:36 hauke Exp $	*/
      2 
      3 /*-
      4  * Copyright (C) 1993	Allen K. Briggs, Chris P. Caputo,
      5  *			Michael L. Finch, Bradley A. Grantham, and
      6  *			Lawrence A. Kesteloot
      7  * All rights reserved.
      8  *
      9  * Redistribution and use in source and binary forms, with or without
     10  * modification, are permitted provided that the following conditions
     11  * are met:
     12  * 1. Redistributions of source code must retain the above copyright
     13  *    notice, this list of conditions and the following disclaimer.
     14  * 2. Redistributions in binary form must reproduce the above copyright
     15  *    notice, this list of conditions and the following disclaimer in the
     16  *    documentation and/or other materials provided with the distribution.
     17  * 3. All advertising materials mentioning features or use of this software
     18  *    must display the following acknowledgement:
     19  *	This product includes software developed by the Alice Group.
     20  * 4. The names of the Alice Group or any of its members may not be used
     21  *    to endorse or promote products derived from this software without
     22  *    specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE ALICE GROUP ``AS IS'' AND ANY EXPRESS OR
     25  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     26  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     27  * IN NO EVENT SHALL THE ALICE GROUP BE LIABLE FOR ANY DIRECT, INDIRECT,
     28  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     29  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     30  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     31  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     32  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     33  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     34  *
     35  */
     36 
     37 /*
     38  * The Macintosh 6522 VIAs are provided with a 783360 Hz E clock that
     39  * used to be 1/10 of the 68000 clock. On the Macintosh II family and
     40  * later models, the E clock is not provided by the 68020+ cpu, but
     41  * generated by the board chipset, in sync with CPU access.
     42  * (Guide to the Macintosh Family Hardware, 2nd Ed., p.149)
     43  */
     44 #define CLK_FREQ	783360		/* VIA clock frequency (Hz) */
     45 
     46 /* Clock needed to hit HZ ticks/sec. */
     47 #define CLK_INTERVAL	((unsigned int)(CLK_FREQ / hz))
     48 
     49 #define CLK_INTH	((CLK_INTERVAL >> 8) & 0xff)	/* high byte */
     50 #define CLK_INTL	(CLK_INTERVAL & 0xff)		/* low byte */
     51 
     52 #if !defined(PRF_INTERVAL)
     53 #define PRF_INTERVAL CLK_INTERVAL
     54 #endif
     55