EX_STWT.C
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/////////////////////////////////////////////////////////////////////////
//// EX_STWT.C ////
//// ////
//// This program uses the RTCC (timer0) and interrupts to keep a ////
//// real time seconds counter. A simple stop watch function is ////
//// then implemented. ////
//// ////
//// Configure the CCS prototype card as described below. ////
//// ////
//// This example will work with the PCM and PCH compilers. The ////
//// following conditional compilation lines are used to include a ////
//// valid device for each compiler. Change the device, clock and ////
//// RS232 pins for your hardware if needed. ////
/////////////////////////////////////////////////////////////////////////
//// (C) Copyright 1996,2001 Custom Computer Services ////
//// This source code may only be used by licensed users of the CCS ////
//// C compiler. This source code may only be distributed to other ////
//// licensed users of the CCS C compiler. No other use, ////
//// reproduction or distribution is permitted without written ////
//// permission. Derivative programs created using this software ////
//// in object code form are not restricted in any way. ////
/////////////////////////////////////////////////////////////////////////
#if defined(__PCM__)
#include <16c74.h>
#fuses HS,NOWDT,NOPROTECT
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7) // Jumpers: 8 to 11, 7 to 12
#elif defined(__PCH__)
#include <18c452.h>
#fuses HS,NOPROTECT
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7) // Jumpers: 8 to 11, 7 to 12
#endif
#define INTS_PER_SECOND 76 // (20000000/(4*256*256))
byte seconds; // A running seconds counter
byte int_count; // Number of interrupts left before a second has elapsed
#int_rtcc // This function is called every time
clock_isr() { // the RTCC (timer0) overflows (255->0).
// For this program this is apx 76 times
if(--int_count==0) { // per second.
++seconds;
int_count=INTS_PER_SECOND;
}
}
main() {
byte start;
int_count=INTS_PER_SECOND;
set_timer0(0);
setup_counters( RTCC_INTERNAL, RTCC_DIV_256);
enable_interrupts(INT_RTCC);
enable_interrupts(GLOBAL);
do {
printf("Press any key to begin.\n\r");
getc();
start=seconds;
printf("Press any key to stop.\n\r");
getc();
printf("%u seconds.\n\r",seconds-start);
} while (TRUE);
}
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