Page 447 - Programming Microcontrollers in C

432 Chapter 8 MCORE, A RISC Machine

Every function in the program with the exception of main() has a
function prototype at the beginning of the program. In this case, the
functions are all void functions that require no arguments. It is
important, however, that every programmer get into the habit of
placing these prototypes at the beginning of their programs, either in
the form of a header file or a direct listing in the program.

Keyboard

The MMC2001 chip has a built-in keyboard interface. This
interface can be either synchronously polled by the program, or it
can be asynchronously controlled through the use of an interrupt.
We will examine the asynchronous control here. This program requires
three parts. The first is the initialization routine. This routine sets up
the operation of the keyboard to cause an interrupt whenever a key is
depressed. The interrupt service detects which key is depressed and
saves it in a buffer. The program also saves a semaphore passed to
the initialization routine. This semaphore is released when the end of
a line is detected in the input. Then the main program prints the
buffer to the terminal screen.
The initialization routine is shown below:
#include “mmc2001.h”
#include “keypad.h”
#include “intctl.h”

static int semaph;
static BYTE *data,*savedata;
static int leng;

/* key board initialization routine */
void kpinit(int sem, BYTE *s, int length)
{

KPCRN.LOROWS=0xf; /* enable keypad rows */
KPDRB.COLUMNS=0x0; /* write 0 to KPDR[15:8] */
KPCRN.LOCOLS=0xf; /* make cols open drain */
KDDRN.LOCOLS=0xf; /* make cols outputs */
KDDRN.LOROWS=0x0; /* and rows inputs */
KPSR.KPKD=ON; /* clear KPKD status flag */
KPSR.KDSC=ON; /* clear key depress synchronizer */
KPSR.KDIE=ON; /* set KDIE bit to enable depress
Interrupt */