How to access the 24LC256 simeltaneously using 2 pics ?

arunb · Joined: 08 Sep 2003 Posts: 492 Location: India

Hi,

Is it possible to access a memory like the 24LC256 from two PICs.

I need to implement a system that logs data and also sends the data to a PC simultaneously (or almost)....

thanks
arunb

treitmey · Joined: 23 Jan 2004 Posts: 1094 Location: Appleton,WI USA

I have done it with a I2C RIC FM24C04 Fram.
It was used by 2 16F877a,within 6" of each other, running off the same clock and power.

I think I would be possible with any I2C.

I had an extra pin to both pics with a pull-up to indicate
the chip was in use. ie: pull the pin down before using the eprom.

Don't "double up" the pull-up resisters. 1 on sda and 1 on scl should do.

rnielsen · Joined: 23 Sep 2003 Posts: 852 Location: Utah

You're, simply, talking about a multi-master system. Each master will be able to talk to any I2C device on the bus, just not at the same time. They'll each need to take control of the I2C bus and take turns. Read up on how multi-master setups work and have fun experimenting.

Ronald