[参考译文] TMS320F2812：CPU 时钟延迟

在以下路径中安装 F281x 的工具包后可以找到此文件：C：\tidcs\c28\DSP281x\v111\DSP281x_common\source\

以下是文件本身 DSP281x_usDelay.asm 的注释

;//###########################################################################
;//
;// 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
;//
;//