Page 323 - Programming Microcontrollers in C

308 Chapter 6 Large Microcontrollers

/* External variables */
WORD pwm_period=0x1000, pwm_count=0x0800,new_input=0;
BYTE new_character;

main()
{
/* The initialization portion of the program */

/* initialize the SIM registers */
SYNCR.X=ON; /* set the system freq to 16.78 mHz */
SYPCR.SWE=OFF; /* disable the watchdog */
/* initialize the GPT */
GPT_MCR.IARB=GPT_IARB;/* pick an IARB for the timers */
ICR.IRL=GPT_IRL; /* interrupt level 6 */
ICR.VBA=GPT_VBA; /* vectors start at 0x40 */
OC1M.OC1M3=ON; /* sent OC1 out to pin */
OC1M.OC1M5=ON; /* couple OC1 to OC3 */
TMSK1.OC3I=ON; /* enable the OC3 interrupt */
OC1D.OC1D5=ON; /* turn on OC3 when OC1 occurs */
TCTL1.OL3=ON; /* toggle OC3 when OC3 occurs */
TOC1=TCNT+pwm_period; /* set OC1 to the period */
TOC3=TOC1+pwm_count; /* set OC3 time on */

/* initialize the SCI
*/
SCCR0.SCBR=BAUD_SET;
/* set baud rate to 9600 */
SCCR2.TE=ON;
/* enable the transmit and */
SCCR2.RE=ON;
/* receiver of the SCI */

cli(); /* enable the system interrupts */

/* the applications portion of the program */

FOREVER
{
if (SCSR.RDRF==ON) /* read in data if it is there */
{
new_character=SCDR; /* get new byte, reset RDRF */
while(SCSR.TDRE==OFF) /* wait until transmit
buffer empty */
SCDR=new_character; /* send out byte and reset TDRE */
/* got an input, process it */
if(new_character>=’0'&&new_character<=’9')
new_input=10*new_input+new_character-’0';
else if(new_character==’\r’)
{
/* reject any number out of range */