110 lines
4.2 KiB
NASM
110 lines
4.2 KiB
NASM
;//###########################################################################
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;//
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;// FILE: F2837xD_usDelay.asm
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;//
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;// TITLE: Simple delay function
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;//
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;// DESCRIPTION:
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;// This is a simple delay function that can be used to insert a specified
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;// delay into code.
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;// This function is only accurate if executed from internal zero-waitstate
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;// SARAM. If it is executed from waitstate memory then the delay will be
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;// longer then specified.
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;// To use this function:
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;// 1 - update the CPU clock speed in the F2837xD_Examples.h
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;// file. For example:
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;// #define CPU_RATE 6.667L // for a 150MHz CPU clock speed
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;// 2 - Call this function by using the DELAY_US(A) macro
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;// that is defined in the F2837xD_Device.h file. This macro
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;// will convert the number of microseconds specified
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;// into a loop count for use with this function.
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;// This count will be based on the CPU frequency you specify.
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;// 3 - For the most accurate delay
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;// - Execute this function in 0 waitstate RAM.
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;// - Disable interrupts before calling the function
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;// If you do not disable interrupts, then think of
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;// this as an "at least" delay function as the actual
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;// delay may be longer.
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;// The C assembly call from the DELAY_US(time) macro will
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;// look as follows:
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;// extern void Delay(long LoopCount);
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;// MOV AL,#LowLoopCount
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;// MOV AH,#HighLoopCount
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;// LCR _Delay
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;// Or as follows (if count is less then 16-bits):
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;// MOV ACC,#LoopCount
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;// LCR _Delay
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;//
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;//###########################################################################
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;//
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;// $Release Date: $
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;// $Copyright:
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;// Copyright (C) 2013-2023 Texas Instruments Incorporated - http://www.ti.com/
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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
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;// 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
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;// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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;// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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;// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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;// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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;// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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;// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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;// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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;// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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;// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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;// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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;// $
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;//###########################################################################
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.if __TI_EABI__
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.asg F28x_usDelay, _F28x_usDelay
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.endif
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.def _F28x_usDelay
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.cdecls LIST ;;Used to populate __TI_COMPILER_VERSION__ macro
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%{
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%}
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.if __TI_COMPILER_VERSION__
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.if __TI_COMPILER_VERSION__ >= 15009000
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.sect ".TI.ramfunc" ;;Used with compiler v15.9.0 and newer
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.else
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.sect "ramfuncs" ;;Used with compilers older than v15.9.0
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.endif
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.endif
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.global __F28x_usDelay
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_F28x_usDelay:
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SUB ACC,#1
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BF _F28x_usDelay,GEQ ;; Loop if ACC >= 0
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LRETR
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;There is a 9/10 cycle overhead and each loop
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;takes five cycles. The LoopCount is given by
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;the following formula:
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; DELAY_CPU_CYCLES = 9 + 5*LoopCount
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; LoopCount = (DELAY_CPU_CYCLES - 9) / 5
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; The macro DELAY_US(A) performs this calculation for you
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;
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;
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;//
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;// End of file
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;//
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