Page 325 - Programming Microcontrollers in C

310 Chapter 6 Large Microcontrollers

This program is a minimum SCI system. The SCI portion of
this chip has comprehensive capabilities that are not exploited in the
program above. These capabilities and error-checking devices are all
available on the chip, and their access anduse is explained in detail in
the QSM Reference Manual. Access of the various capabilities is
exactly the same as was shown above in this program.

Periodic Interrupt

To make the problem a little more interesting, let’s add another
load to the machine by making use of the periodic interrupt capabil­
ity provided in the SIM to create an interrupt. With this interrupt, we
will build a time-of-day clock similar to that developed in Chapter 4.
In this case you will see that the applications code developed for the
MC68HC05 will work fine for the MC68HC16. Of course, the ini­
tialization code and the interrupt service routine will be completely
different for the MC68HC16. This additional code will be put right
into the program listed in Listing 6-3. It is asserted that there will be
no adverse interactions between the various sections of the code.
#include “hc16z1.h”
#include “gpt.h”
#include “sim.h”
#include “qsm.h”
#include “defines.h”

#define PERIOD 0x1000
#define ON_TIME 0x0800
#define SIM_IARB 4
#define PIC_PIRQL 6
#define PIC_PIV 0X38
#define PIT_PITM 16
#define GPT_IARB 10
#define GPT_IRL 6
#define GPT_VBA 5
/* set the baud rate=fclock/32*baud_rate */
#define BAUD_SET (32768*512)/(32*38400)
#define TIME_COUNT 1000
#define MAX_MIN 59
#define MAX_HOURS 12
#define MIN_HOURS 1
#define NO_WAIT 0
#define OC2_OFFSET 5
#define MAX_SEC 59