waitusec.c

日本著名的的嵌入式实时操作系统T-Kernel的源码及用户手册。

/*
 *----------------------------------------------------------------------
 *    T-Kernel
 *
 *    Copyright (C) 2004 by Ken Sakamura. All rights reserved.
 *    T-Kernel is distributed under the T-License.
 *----------------------------------------------------------------------
 *
 *    Version:   1.01.00
 *    Released by T-Engine Forum(http://www.t-engine.org) at 2004/6/28.
 *
 *----------------------------------------------------------------------
 */

/*
 *	@(#)waitusec.c (libtk/VR4131)
 *
 *	Busy loop wait time in micro-sec  
 */

#include <basic.h>
#include <sys/sysinfo.h>

EXPORT void WaitUsec( UINT usec )
{
	UW	count = usec * SCInfo.loop64us / 64;

	Asm("		.set	push		\n"
	"		.set	noreorder	\n"
	"	loop:	bnez	%0, loop	\n"
	"		subu	%0, %0, 1	\n"
	"		.set	pop		"
		: "=r"(count)
		: "0"(count)
	);
}