;// TI File $Revision: /main/2 $
;// Checkin $Date: April 29, 2005 11:01:42 $
;//###########################################################################
;//
;// FILE: DSP281x_usDelay.asm
;//
;// TITLE: Simple delay function
;//
;// DESCRIPTION:
;//
;// This is a simple delay function that can be used to insert a specified
;// delay into code.
;//
;// This function is only accurate if executed from internal zero-waitstate
;// SARAM. If it is executed from waitstate memory then the delay will be
;// longer then specified.
;//
;// To use this function:
;//
;// 1 - update the CPU clock speed in the DSP281x_Examples.h
;// file. For example:
;// #define CPU_CLOCK_SPEED 6.6667L // for a 150MHz CPU clock speed
;//
;// 2 - Call this function by using the DELAY_US(A) macro
;// that is defined in the DSP28_Device.h file. This macro
;// will convert the number of microseconds specified
;// into a loop count for use with this function.
;// This count will be based on the CPU frequency you specify.
;//
;// 3 - For the most accurate delay
;// - Execute this function in 0 waitstate RAM.
;// - Disable interrupts before calling the function
;// If you do not disable interrupts, then think of
;// this as an "at least" delay function as the actual
;// delay may be longer.
;//
;// The C assembly call from the DELAY_US(time) macro will
;// look as follows:
;//
;// extern void Delay(long LoopCount);
;//
;// MOV AL,#LowLoopCount
;// MOV AH,#HighLoopCount
;// LCR _Delay
;//
;// Or as follows (if count is less then 16-bits):
;//
;// MOV ACC,#LoopCount
;// LCR _Delay
;//
;//
;//###########################################################################
;// $TI Release: DSP281x C/C++ Header Files V1.20 $
;// $Release Date: July 27, 2009 $
;//###########################################################################
.def _DSP28x_usDelay
.sect "ramfuncs"
.global __DSP28x_usDelay
_DSP28x_usDelay:
SUB ACC,#1
BF _DSP28x_usDelay,GEQ ;; Loop if ACC >= 0
LRETR
;There is a 9/10 cycle overhead and each loop
;takes five cycles. The LoopCount is given by
;the following formula:
; DELAY_CPU_CYCLES = 9 + 5*LoopCount
; LoopCount = (DELAY_CPU_CYCLES - 9) / 5
; The macro DELAY_US(A) performs this calculation for you
;==================================================
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