PIC 16F877 - identifying external EEPROM

Hi,

I am failry new to this game and would appreciate some help if anyone can.

I am currently making an magnetometer which uses a 16F877-20 with 2 external eeprom chips. I have successfully made one but the second has caused me problems. For some reason on startup the PIC cannot see the EEPROM. Can anyone please tell me how the PIC communicates with the EEPROM and is there anyway I can check that it is functioning properly.

Any ideas would be appreciated.

Many thanks

Presuming they are I2C EEPROM's?, you simply set them to different addresses, and use the address for the one you want to access.

try pullup resistors on the scl & sda lines

Also assuming that they are I2C EEPROMS, make sure that they aren't locked up by sending out a 12 or more clock pulses from the PIC, with the data line is pulled high by the pull-up resistor.

You can get a problem where the EEPROM is in the middle of sending data or an acknowledge, and the PIC is at a different place.

When the pulses are seen by the EEPROM and no data is acknowledged, it will go into its standby state. You can then get the I2C module or the code to start the I2c communication.