Page 294 - Programming Microcontrollers in C

Timer Operations 279

This sequence repeats each half second until in_process is set to
TRUE. Whenever a character is read in through the serial port,
in_process is set to TRUE to disable the continual output from
the system while a new input speed value is being entered. If there is
a new character in the input buffer, this character is read in and the
RDRF flag is reset. The new character is immediately echoed back to
the sending device as part of full duplex operation. If the new character
is a digit it is processed, if it is a line feed it is also processed, and any
number string is converted to an integer so that it can be used by the
computer. The size of the number is tested to be certain that it is
within the acceptable speed limits for the motor, and if it passes all
of the tests, it is placed in the variable location motor_speed to
indicate that a new motor speed is here and should be processed.

#include “hc11e9.h”

#define DIVIDE_8_SHIFT 3
#define COUNT_8 8
#define COUNT_MAX 3300
#define COUNT_MIN 1600
#define COUNT_ONE_QUARTER 32
#define COUNT_ONE_SECOND 128
#define PERIOD 0X1000
#define TIME_ON 0x0800
#define IMPOSSIBLE 3500
#define TOO_LOW 100
#define RPM_MIN 1000
#define RPM_MAX 11000
#define CR 0x0d
#define LF 0x0a

/*function prototypes */
@port void IC1_Isr(void);
@port void OC2_Isr(void);
@port void OC3_Isr(void);
int putchar(char new_character);
void dprint (unsigned int c);
void do_crlf(void);
long limit(long );