// memory interface file

#include <Mega32.h>
#include <delay.h>

#define ADDREN PORTD.2
#define WE PORTD.5
#define DATACLK PORTD.3
#define ADDRCLK PORTD.4
#define OUTB PORTC                
	unsigned short int result2;

//#define MEMDEBUG

void initmem(void) {
	DDRC=0xff; // 8 bit output to buffers
	DDRA=0x00; // input from chip
	DDRB=0x00; // input from chip
	DDRD.0=0;
	DDRD.1=1;
	DDRD.2=1; // ADDREN (fed thru an inverter to addr buffers)
	DDRD.3=1; // DATACLK (pos pulse=lo byte written)
	DDRD.4=1; // ADDRCLK (pos pulse=lo byte written)
	DDRD.5=1; // WE (fed thru an inverter to mem chip and to data buffers)
	DDRD.6=0; // reserved
	DDRD.7=0; // reserved
	OUTB=0;
	ADDREN=0;
	WE=0;         
	DATACLK=0; // clock in zeros into buffers
	ADDRCLK=0;
	DATACLK=1;
	ADDRCLK=1;
	DATACLK=0;
	ADDRCLK=0;
}  

void writeaddr(unsigned short int a) {
	unsigned char lo,hi;
	lo=a&0xff;
	hi=a>>8; 
	
	ADDRCLK=0; // set initial state of addr clk
	delay_us(2);
	OUTB=lo;    
	delay_us(2);	
	ADDRCLK=1; // clock in low byte
	delay_us(2);	
	OUTB=hi;
	delay_us(2);	
	ADDRCLK=0; // clock in high byte
	delay_us(2);	
}          

void writedata(unsigned short int a) {
	unsigned char lo,hi;
	lo=a&0xff;
	hi=a>>8;
	
	DATACLK=0; // set initial state of addr clk
	delay_us(2);
	OUTB=lo;    
	delay_us(2);	
	DATACLK=1; // clock in low byte
	delay_us(2);
	OUTB=hi;
	delay_us(2);
	DATACLK=0; // clock in high byte
	delay_us(2);
}          

unsigned short int memwrite(unsigned short int addr, unsigned short int val) {
	unsigned short int result;
	WE=0;
	// fill the buffers 
	ADDREN=1;
	writeaddr(addr);   
	delay_us(2);
	WE=1;
	writedata(val);           
	delay_us(2);
	// execute the write
	delay_us(2);    
	// return DATA lines to double check
	result=PINA|(((unsigned short)PINB)<<8);
	WE=0;
	delay_us(2);
	ADDREN=0; 
	delay_us(2);		
	return result;
}

unsigned short int memread(unsigned short int addr) {
	unsigned short int result;
	WE=0;
	ADDREN=1;                           
	// write addr to read from
	writeaddr(addr);  
//	ADDREN=1;
	delay_us(5);              
	// read it
	result=(((unsigned short int)PINB)<<8)|(PINA);
	ADDREN=0;
	return result;
}
#ifdef MEMDEBUG // for memory testing
void main(void) {
	initmem();   
	writedata(0xffff);    
	writeaddr(0x0000);
	ADDREN=1;
	WE=1;
	while(1);
}  
#endif