Post by thread:24c02 eeprom read problems

Pleeease HELP ! I am unable to read the information in an 24C02 eeprom, I can successfully write to any address, but all reads return a 'FF', irrelevant of the information held in them, which I know to be valid data. How can I set the port up to read instead of write on the data lines esp. DATA_0(pin 2) Regards, Simon unsigned char in_byte(void) /* fetch byte, most significant bit first */ { unsigned char i_byte=0x00; int n; SetPortReadmode(); <------------ set bit 5 of control port to 1 high_SDA(); for (n=0; n<8; n++) { high_SCL(); i_byte=(i_byte << 1) | (inportb(DATA)); low_SCL(); } SetPortWritemode(); <------------ set bit 5 of control port to 0 return(i_byte); }

Simon Says: In a message dated 6/23/99 4:07:29 PM Pacific Daylight Time, spam_OUTspredwoodTakeThisOuTsri-net.demon.co.uk writes: > Pleeease HELP ! > > I am unable to read the information in an 24C02 eeprom, I can successfully > write to any address, but all reads return a 'FF', irrelevant of the > information held in them, which I know to be valid data. > > How can I set the port up to read instead of write on the data lines esp. > DATA_0(pin 2) Hi Simon, Is this interface to a PIC or parallel port? If it's to a parallel port, and you want to use the DATA lines as input, make sure your port is set to EPP or ECP. Then, you'll need to set bit 5 of the control port, in pseudo code, it'd be something like this: Out to Control Port = Control Port (37A on some puters) OR &H20 This will set all 8 data lines to input. As far as the I2C read routines, can't help ya there, I've never implemented I2C on the parallel port -- I got too darn frustrated with it and put it on hold. Hope this helps, Tim H.

Hi, look at the comment inserted below. I hope it will help you. Imre On Thu, 24 Jun 1999, Simon Redwood wrote: {Quote hidden}> Pleeease HELP ! > > I am unable to read the information in an 24C02 eeprom, I can successfully > write to any address, but all reads return a 'FF', irrelevant of the > information held in them, which I know to be valid data. > > How can I set the port up to read instead of write on the data lines esp. > DATA_0(pin 2) > > > Regards, > Simon > > unsigned char in_byte(void) > /* fetch byte, most significant bit first */ > { > unsigned char i_byte=0x00; > int n; > > SetPortReadmode(); <------------ set bit 5 of control > port to 1 > high_SDA(); > > for (n=0; n<8; n++) { > high_SCL(); // changing the following line > i_byte=(i_byte << 1) | (inportb(DATA) & 0x01); // actually, you should (and want) to read a single bit instead of // the whole port... {Quote hidden}> low_SCL(); > } > > SetPortWritemode(); <------------ set bit 5 of control > port to 0 > > return(i_byte); > } > >

> Van: Simon Redwood <.....spredwoodKILLspam@spam@sri-net.demon.co.uk> > Aan: PICLISTKILLspamMITVMA.MIT.EDU > Onderwerp: 24c02 eeprom read problems > Datum: donderdag 24 juni 1999 1:04 > > Pleeease HELP ! > > I am unable to read the information in an 24C02 eeprom, I can successfully > write to any address, but all reads return a 'FF', irrelevant of the > information held in them, which I know to be valid data. > > How can I set the port up to read instead of write on the data lines esp. > DATA_0(pin 2) Simon, I did send you an ASCII drawing to interface a 24Cxx to a standard Printer-port connector. Did you receive it ? I'm using it here, connected to the Programming-adapter (IC-foot) with four lose wires of about a meter, and it did not fail me once (in over a year) .. Greetz, Rudy Wieser