#include <reg52.h>
sbit CS=P2^7;
sbit SK=P2^6;
sbit DI=P2^5;
sbit DO=P2^4;

/*
extern unsigned char ReadChar(unsigned char address);
extern void WriteChar(unsigned char address,unsigned char Indata);
extern void ReadString(unsigned char data *RamAddress,unsigned char RomAddress,unsigned char Number);
extern void WriteString(unsigned char data *RamAddress,unsigned char RomAddress,unsigned char Number);
*/

// Write enable must precede all programming modes.
void Ewen(void) {
unsigned char temp,InData;
CS=0;
SK=0;
CS=1;
InData=0x98; // 10011XXXX
for(temp=9;temp!=0;temp--) { // 9
DI=InData&0x80;
SK=1; SK=0;
InData<<=1;
}
CS=0;
}

// Disables all programming instructions.
void Ewds(void) {
unsigned char temp,InData;
CS=0;
SK=0;
CS=1;
InData=0x80; // 10000XXXX
for(temp=9;temp!=0;temp--) { // 9
DI=InData&0x80;
SK=1; SK=0;
InData<<=1;
}
CS=0;
}

// Reads data stored in memory, at specified address.
unsigned int Read(unsigned char address) {
unsigned char temp;
unsigned int result;
Ewen();
SK=0; DI=1; // 110 A5-A0
CS=0; CS=1;
SK=1; SK=0; // 1
address=address&0x3f|0x80;
for(temp=8;temp!=0;temp--) { // 8
DI=address&0x80;
SK=1; SK=0;
address<<=1;
}
DO=1;
for(temp=16;temp!=0;temp--) { // 16
SK=1;
result=(result<<1)|DO;
SK=0;
}
CS=0;
Ewds();
return(result);
}

// Writes memory location An - A0.
void Write(unsigned char address,unsigned int InData) {
unsigned char temp;
Ewen();
SK=0; DI=1; // 101 A5-A0
CS=0; CS=1;
SK=1; SK=0; // 1
address=address&0x3f|0x40;
for(temp=8;temp!=0;temp--) { // 8
DI=address&0x80;
SK=1; SK=0;
address<<=1;
}
for(temp=16;temp!=0;temp--) { // 16
DI=InData&0x8000;
SK=1; SK=0;
InData<<=1;
}
CS=0; DO=1;
CS=1; SK=1;
while(DO==0) { // busy test
SK=0; SK=1;
}
SK=0; CS=0;
Ewds();
}

/*
// Erase memory location An - A0.
void Erase(unsigned char address) {
unsigned char temp;
Ewen();
SK=0; DI=1; // 111 A5-A0
CS=0; CS=1;
SK=1; SK=0; // 1
address|=0xc0;
for(temp=8;temp!=0;temp--) { // 8
DI=address&0x80;
SK=1; SK=0;
address<<=1;
}
CS=0; DO=1;
CS=1; SK=1;
while(DO==0) {
SK=0; SK=1;
}
SK=0; CS=0;
Ewds();
}

// Erases all memory locations. Valid only at VCC = 4.5V to 5.5V.
void Eral(void) {
unsigned char temp,InData;
Ewen();
CS=0;
SK=0;
CS=1;
InData=0x90; // 10010XXXX
for(temp=9;temp!=0;temp--) { // 9
DI=InData&0x80;
SK=1; SK=0;
InData<<=1;
}
CS=0; DO=1;
CS=1; SK=1;
while(DO==0) {
SK=0; SK=1;
}
SK=0; CS=0;
Ewds();
}

// Writes all memory locations. Valid only at VCC = 4.5V to 5.5V.
void Wral(unsigned int InData) {
unsigned char temp,address;
Ewen();
CS=0;
SK=0;
CS=1;
address=0x88; // 10001XXXX
for(temp=9;temp!=0;temp--) { // 9
DI=address&0x80;
SK=1; SK=0;
address<<=1;
}
for(temp=16;temp!=0;temp--) { // 16
DI=InData&0x8000;
SK=1; SK=0;
InData<<=1;
}
CS=0; DO=1;
CS=1; SK=1;
while(DO==0) {
SK=0; SK=1;
}
SK=0; CS=0;
Ewds();
}

*/

unsigned char ReadChar(unsigned char address) {
unsigned char temp=address>>1;
if(address&0x01) return((unsigned char)(Read(temp)>>8));
else return((unsigned char)(Read(temp)));
}

void WriteChar(unsigned char address,unsigned char InData) {
unsigned char temp=address>>1;
if(address&0x01) Write(temp,(unsigned int)(Read(temp)&0x00ff|(InData<<8)));
else Write(temp,(unsigned int)(Read(temp)&0xff00|InData));
}

void ReadString(unsigned char data *RamAddress,unsigned char RomAddress,unsigned char Number) {
while(Number!=0) {
*RamAddress=ReadChar(RomAddress);
RamAddress++;
RomAddress++;
Number--;
}
}

void WriteString(unsigned char data *RamAddress,unsigned char RomAddress,unsigned char Number) {
unsigned int temp;
if(Number==0) return;
if(RomAddress&0x01) {
WriteChar(RomAddress,*RamAddress);
RamAddress++;
RomAddress++;
Number--;
}
if(Number==0) return;
while(Number>>1) {
temp=*RamAddress;
RamAddress++;
temp=temp|(*RamAddress)<<8;
RamAddress++;
Write(RomAddress>>1,temp);
RomAddress++;
RomAddress++;
Number--;
Number--;
}
if(Number) WriteChar(RomAddress,*RamAddress);
}