68 lines
2.7 KiB
Groff
68 lines
2.7 KiB
Groff
.\" $NetBSD: delay.9,v 1.4 2003/04/16 13:35:27 wiz Exp $
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.\"
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.\" Copyright (c) 2002 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Gregory McGarry.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd May 23, 2002
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.Dt DELAY 9
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.Os
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.Sh NAME
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.Nm delay ,
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.Nm DELAY
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.Nd microsecond delay
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.Sh SYNOPSIS
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.In machine/param.h
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.Ft void
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.Fn delay "unsigned int us"
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.Ft void
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.Fn DELAY "unsigned int us"
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.Sh DESCRIPTION
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Wait approximately
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.Fa us
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microseconds.
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.Pp
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The delay is implemented as a machine loop, preventing events other than
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interrupt handlers for unmasked interrupts to run.
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.Fn DELAY
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is reentrant (doesn't modify any global kernel or machine state) and is
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safe to use in interrupt or process context.
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.Pp
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For long delays,
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.Xr tsleep 9
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should be considered, however it can only be called from process context
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and its resolution is limited by the system clock frequency.
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.Sh SEE ALSO
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.Xr hz 9 ,
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.Xr tsleep 9
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