Lpc2000

George,

The I/O pins are 5V tolerant and the I2C pins have open drain outputs.
So  to  answer Q1: You may pull the pins to 5 volt, creating a 5 volt 
I2C interface for your PICs.

An answer on Q2 depends a bit on the type of cable used in combination 
with bus termination.
I do not think however that a100 or 400 kHz clock will be a problem.
If you are woried about bus errors, check the amount of traffic that 
passes over the bus and the response times you need and  adapt your 
clock to be the lowest allowable value. I.e: if writing an output to the 
PIC needs 5 bytes (slave addr + 4 data) this uses 47 clocks (start bit + 
4x9 + stop bit) and if this needs to complete within 10 ms which results 
in a 4.7 kHz clock (3 of these on one bus result in 14.1 kHz).

Regards,

    Rob


George M. Gallant, Jr. wrote:

>I want to add a lpc2214 to an existing robot that currently has 3
>18f252's connected via
>I2C. The LPC would become that MASTER and the PIC's become peripherals.
>The PIC's
>are at 5V due to external sensors and control circuits. 
>
>Questions: 1. What voltage shoudl the SDA & SCL be pulled up to?
>                  2. Max clock rate for 10inch (25cm) cable?
>  
>