16F874A and 24C64 problem with writting 1800-1FFF

[Bieli]

PCM 3.091
16F874 + Atmel 24C64
I can't write data between address 1800-1FFF. On lower addresses 0000-17FF it work fine but higher not. Read function work, I can read data on this area, but I can't change it. I second 24C64 chip and it has this same.


#include <16f874a.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP,NOBROWNOUT
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)

#define I2C_SDA PIN_C4
#define I2C_SCL PIN_C3

#use i2c(master,sda=I2C_SDA, scl=I2C_SCL)

#include <input.c>

void init_ext_eeprom() {
output_float(I2C_SCL);
output_float(I2C_SDA);
}


void write_ext_eeprom(long int address, byte data)
{
i2c_start();
i2c_write(0xa2);
i2c_write(address>>8);
i2c_write(address);
i2c_write(data);
i2c_stop();
delay_ms(10);
}


byte read_ext_eeprom(long int address)
{
byte data;
i2c_start();
i2c_write(0xa2);
i2c_write(address>>8);
i2c_write(address);
i2c_start();
i2c_write(0xa3);
data=i2c_read(0);
i2c_stop();
return(data);
}

main()
{byte value,cmd;
long address;


init_ext_eeprom();

while(1)
{ do
{ printf("\r\nRead or Write: ");
cmd=getc();
cmd=toupper(cmd);
putc(cmd);
} while ( (cmd!='R') && (cmd!='W') );

printf("\n\rLocation: ");

address = gethex();
address = (address<<8)+gethex();
if(cmd=='R')
printf("\r\nValue: \%X\r\n",READ_EXT_EEPROM( address ) );

if(cmd=='W')
{ printf("\r\nNew value: ");
value = gethex();
printf("\n\r");
WRITE_EXT_EEPROM( address, value );
}
}
}


Bieli
___________________________
This message was ported from CCS's old forum
Original Post ID: 144515255

[Tomi]

I didn't use 24C64 in the last two years but as I remember this chip has a "block write protect" feature and the default page is somewhere in the upper address space. Check the datasheet.

:=PCM 3.091
:=16F874 + Atmel 24C64
:=I can't write data between address 1800-1FFF. On lower addresses 0000-17FF it work fine but higher not. Read function work, I can read data on this area, but I can't change it. I second 24C64 chip and it has this same.
:=
:=
:=#include <16f874a.h>
:=#fuses HS,NOWDT,NOPROTECT,NOLVP,NOBROWNOUT
:=#use delay(clock=4000000)
:=#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
:=
:=#define I2C_SDA PIN_C4
:=#define I2C_SCL PIN_C3
:=
:=#use i2c(master,sda=I2C_SDA, scl=I2C_SCL)
:=
:=#include <input.c>
:=
:=void init_ext_eeprom() {
:= output_float(I2C_SCL);
:= output_float(I2C_SDA);
:=}
:=
:=
:=void write_ext_eeprom(long int address, byte data)
:={
:= i2c_start();
:= i2c_write(0xa2);
:= i2c_write(address>>8);
:= i2c_write(address);
:= i2c_write(data);
:= i2c_stop();
:= delay_ms(10);
:=}
:=
:=
:=byte read_ext_eeprom(long int address)
:={
:= byte data;
:= i2c_start();
:= i2c_write(0xa2);
:= i2c_write(address>>8);
:= i2c_write(address);
:= i2c_start();
:= i2c_write(0xa3);
:= data=i2c_read(0);
:= i2c_stop();
:= return(data);
:=}
:=
:=main()
:={byte value,cmd;
:=long address;
:=
:=
:= init_ext_eeprom();
:=
:=while(1)
:={ do
:= { printf("\r\nRead or Write: ");
:= cmd=getc();
:= cmd=toupper(cmd);
:= putc(cmd);
:= } while ( (cmd!='R') && (cmd!='W') );
:=
:= printf("\n\rLocation: ");
:=
:= address = gethex();
:= address = (address<<8)+gethex();
:= if(cmd=='R')
:= printf("\r\nValue: \%X\r\n",READ_EXT_EEPROM( address ) );
:=
:= if(cmd=='W')
:= { printf("\r\nNew value: ");
:= value = gethex();
:= printf("\n\r");
:= WRITE_EXT_EEPROM( address, value );
:= }
:=}
:=}
:=
:=
:=Bieli
___________________________
This message was ported from CCS's old forum
Original Post ID: 144515258

[Felix Althaus]

Hello

From the datasheet:
WRITE PROTECT (WP): The write protect input, when tied to GND, allows normal write operations. When WP is tied high to VCC, all write operations to the upper quandrant (8/16K bits) of memory are inhibited. If left unconnected, WP is internally pulled down to GND.

mfg
Felix
___________________________
This message was ported from CCS's old forum
Original Post ID: 144515259