extram.c

fitted with the external ram for avr

/************************************************
 Demonstration program for sccavr: extram.c
 Configures an SDK200 fitted with the external ram
 components. Writes a incrementing number to an array 
 of bytes, then reads it back checking for errors.
 Use avrinit3.s90

 Ron Kreymborg
************************************************/

#include	<avrstdio.h>

#define	BYTE	unsigned char
#define	SIZE	32000

void main(void);
void blink(void);
void delay(void);

BYTE data[SIZE];

void main(void) {
	register BYTE value;
	register int i;
	
	outp(DDRB, 0xff);						// PORTB is output
	value = 1;
	while (1) {								// do forever
		outp(PORTB, ~value);				// show value
		for (i=0; i<SIZE; i++)			// fill data array
			data[i] = value;
		for (i=0; i<SIZE; i++) {
			if (data[i] != value) {		// check all is ok
				outp(PORTB, 0);			// turn all on
				while (1)					// and hang if not
					;
				}
			}
		value++;								// step to next value
		blink();								// blink LED 7
		}
}


// Blink LED 7 on PORTB for a few mSecs.

void blink(void) {
	register BYTE b;
	
	b = inp(PORTB);						// get current value
	outp(PORTB, b | 0x80);				// ensure 7 off
	delay();
	outp(PORTB, b & 0x7f);				// turn it on
	delay();
	outp(PORTB, b);						// restore whatever
}


void delay(void) {
	int i;
	for (i=0; i<4000; i++)				// about 70mS @ 4MHZ
		;
}