62 lines
2.4 KiB
C
62 lines
2.4 KiB
C
/*
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* Copyright (c) 2020, Texas Instruments Incorporated
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* All rights reserved.
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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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*
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* * 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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*
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* * 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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*
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* * Neither the name of Texas Instruments Incorporated nor the names of
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* its 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 COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <stdint.h>
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#include <ti/driverlib/dl_common.h>
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void DL_Common_delayCycles(uint32_t cycles)
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{
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/* this is a scratch register for the compiler to use */
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uint32_t scratch;
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/* There will be a 2 cycle delay here to fetch & decode instructions
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* if branch and linking to this function */
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/* Subtract 2 net cycles for constant offset: +2 cycles for entry jump,
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* +2 cycles for exit, -1 cycle for a shorter loop cycle on the last loop,
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* -1 for this instruction */
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__asm volatile(
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#ifdef __GNUC__
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".syntax unified\n\t"
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#endif
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"SUBS %0, %[numCycles], #2; \n"
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"%=: \n\t"
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"SUBS %0, %0, #4; \n\t"
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"NOP; \n\t"
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"BHS %=b;" /* branches back to the label defined above if number > 0 */
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/* Return: 2 cycles */
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: "=&r"(scratch)
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: [ numCycles ] "r"(cycles));
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}
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