delay.h

Clock+data serial protocol for PIC16/18F processors. Contains an example application for Zoom/Focus/

/*

lowlevel delay routines

Designed by Shane Tolmie of KeyGhost corporation.  Freely distributable.
Questions and comments to [e-mail]
Want to see 4Mb of Hi-Tech C FAQ and sample source code? http://www.keyghost.com/htpic
(also has tiny device to record keystrokes in hardware on PC)

For Microchip 12C67x, 16C7x, 16F87x and Hi-Tech C

Example C:

#define PIC_CLK 8000000

#include "delay.h"

unsigned int timeout_int, timeout_char;

timeout_char=timeout_char_us(1147);
while(timeout_char-- && (RA1==0));  //wait up to 1147us for port RA1 to go high
				    //  - this is the max timeout

timeout_int=timeout_int_us(491512);
while(timeout_int-- && (RA1==0));   //wait up to 491512us for port RA1 to go high
				    //  - this is the max timeout

dly250n;      //delay 250ns
dly1u;        //delay 1us
DelayUs(40);  //do not do DelayUs(0) or else it bombs :)
DelayUs(255); //max

*/

#ifndef __DELAY_H
#define __DELAY_H

#define PIC_CLK 8000000

extern unsigned char delayus_variable;

#if (PIC_CLK == 4000000) || (PIC_CLK == 3686400) //3686400 is not entirely accurate, but it works
	#define dly125n please remove; for 32Mhz+ only
	#define dly250n please remove; for 16Mhz+ only
	#define dly500n please remove; for 8Mhz+ only
	#define dly1u asm("nop")
	#define dly2u dly1u;dly1u
#elif (PIC_CLK == 8000000)
	#define dly125n please remove; for 32Mhz+ only
	#define dly250n please remove; for 16Mhz+ only
	#define dly500n asm("nop")
	#define dly1u dly500n;dly500n
	#define dly2u dly1u;dly1u
#elif ( (PIC_CLK == 16000000) || (PIC_CLK == 16257000) )
	#define dly125n please remove; for 32Mhz+ only
	#define dly250n asm("nop")
	#define dly500n dly250n;dly250n
	#define dly1u dly500n;dly500n
	#define dly2u dly1u;dly1u
#elif (PIC_CLK == 20000000)
	#define dly200n asm("nop")
	#define dly400n dly250n;dly250n
	#define dly2u dly400n;dly400n;dly400n;dly400n;dly400n
#elif (PIC_CLK == 32000000)
	#define dly125n asm("nop")
	#define dly250n dly125n;dly125n
	#define dly500n dly250n;dly250n
	#define dly1u dly500n;dly500n
	#define dly2u dly1u;dly1u
#else
	#error please define pic_clk correctly
#endif

//*****
//delay routine

#if PIC_CLK == 4000000 || (PIC_CLK == 3686400) //3686400 is not entirely accurate, but it works
	#define DelayDivisor 4
	#define WaitFor1Us asm("nop")
	#define Jumpback asm("goto $ - 2")
#elif PIC_CLK == 8000000
	#define DelayDivisor 2
	#define WaitFor1Us asm("nop")
	#define Jumpback asm("goto $ - 2")
#elif ( (PIC_CLK == 16000000) || (PIC_CLK==16257000) )
	#define DelayDivisor 1
	#define WaitFor1Us asm("nop")
	#define Jumpback asm("goto $ - 2")
#elif PIC_CLK == 20000000
	#define DelayDivisor 1
	#define WaitFor1Us asm("nop")
	#define WaitFor1Us asm("nop")	
	#define Jumpback asm("goto $ - 2")
#elif PIC_CLK == 32000000
	#define DelayDivisor 1
	#define WaitFor1Us asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop")
	#define Jumpback asm("goto $ - 6")
#else
	#error please define pic_clk correctly
#endif

#define DelayUs(x) { \
			delayus_variable=(unsigned char)(x/DelayDivisor); \
			WaitFor1Us; } \
			asm("decfsz _delayus_variable,f"); \
			Jumpback;

/*

timeouts:

C code for testing with ints:

			unsigned int timeout;
			timeout=4000;
			PORT_DIRECTION=OUTPUT;
			while(1)
			{
				PORT=1;
				timeout=8000;
				while(timeout-- >= 1);	//60ms @ 8Mhz, opt on, 72ms @ 8Mhz, opt off
				PORT=0;
			}

Time taken:	optimisations on:		16cyc/number loop, 8us @ 8Mhz
			optimisations off:		18cyc/number loop, 9us @ 8Mhz
			with extra check ie:	&& (RB7==1), +3cyc/number loop, +1.5us @ 8Mhz

C code for testing with chars:

			similar to above

Time taken:	optimisations on:		9cyc/number loop, 4.5us @ 8Mhz
			with extra check ie:	&& (RB7==1), +3cyc/number loop, +1.5us @ 8Mhz

Formula:	rough timeout value = (<us desired>/<cycles per loop>) * (PIC_CLK/4.0)

To use:		//for max  timeout of 1147us @ 8Mhz
			#define LOOP_CYCLES_CHAR	9					//how many cycles per loop, optimizations on
			#define timeout_char_us(x)	(unsigned char)((x/LOOP_CYCLES_CHAR)*(PIC_CLK/4.0))
			unsigned char timeout;
			timeout=timeout_char_us(1147);						//max timeout allowed @ 8Mhz, 573us @ 16Mhz
			while((timeout-- >= 1) && (<extra condition>));	//wait

To use:		//for max 491512us, half sec timeout @ 8Mhz
			#define LOOP_CYCLES_INT		16					//how many cycles per loop, optimizations on
			#define timeout_int_us(x)	(unsigned int)((x+/LOOP_CYCLES_INT)*(PIC_CLK/4.0))
			unsigned int timeout;
			timeout=timeout_int_us(491512);						//max timeout allowed @ 8Mhz
			while((timeout-- >= 1) && (<extra condition>));	//wait
*/
#define LOOP_CYCLES_CHAR	9							//how many cycles per loop, optimizations on
#define timeout_char_us(x)	(unsigned char)((x/LOOP_CYCLES_CHAR)*(PIC_CLK/4000000.0))

#define LOOP_CYCLES_INT		16							//how many cycles per loop, optimizations on
#define timeout_int_us(x)	(unsigned int)((x/LOOP_CYCLES_INT)*(PIC_CLK/4000000.0))

void DelayBigUs(unsigned int cnt);
void DelayMs(unsigned char cnt);
void DelayBigMs(unsigned int cnt);

#endif