hi-tech delay
a) use already written delay routines or write your own
b) under "CPP Pre-defined symbols" add -DXTAL_FREQ=4MHZ (for 4MHZ crystal)
c) I dunno how precise these two attached routines are, but if you're gonna need very precise delays, write your own code for delays
d) look at b)
remember to put these two files in the same directory as your source files.
Usage: DelayUs(13); or DelayMs(115);
regards,
rfmw
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/* Filename: Delay.c
* Delay functions
* See delay.h for details
*
* Make sure this code is compiled with full optimization!!!
*/
#include "delay.h"
void
DelayMs(unsigned char cnt)
{
#if XTAL_FREQ <= 2MHZ
do {
DelayUs(996);
} while(--cnt);
#endif
#if XTAL_FREQ > 2MHZ
unsigned char i;
do {
i = 4;
do {
DelayUs(250);
} while(--i);
} while(--cnt);
#endif
}
-----------------------------------------
-----------------------------------------
/* Filename: Delay.h
* Delay functions for HI-TECH C on the PIC
*
* Functions available:
* DelayUs(x) Delay specified number of microseconds
* DelayMs(x) Delay specified number of milliseconds
*
* Note that there are range limits: x must not exceed 255 - for xtal
* frequencies > 12MHz the range for DelayUs is even smaller.
* To use DelayUs it is only necessary to include this file; to use
* DelayMs you must include delay.c in your project.
*
*/
/* Set the crystal frequency in the CPP predefined symbols list in
HPDPIC, or on the PICC commmand line, e.g.
picc -DXTAL_FREQ=4MHZ
or
picc -DXTAL_FREQ=100KHZ
Note that this is the crystal frequency, the CPU clock is
divided by 4.
* MAKE SURE this code is compiled with full optimization!!!
*/
#ifndef XTAL_FREQ
#define XTAL_FREQ 4MHZ /* Crystal frequency in MHz */
#endif
#define MHZ *1000L /* number of kHz in a MHz */
#define KHZ *1 /* number of kHz in a kHz */
#if XTAL_FREQ >= 12MHZ
#define DelayUs(x) { unsigned char _dcnt; \
_dcnt = (x)*((XTAL_FREQ)/(12MHZ)); \
while(--_dcnt != 0) \
continue; }
#else
#define DelayUs(x) { unsigned char _dcnt; \
_dcnt = (x)/((12MHZ)/(XTAL_FREQ))|1; \
while(--_dcnt != 0) \
continue; }
#endif
extern void DelayMs(unsigned char);
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