Franck, > Where can I get resources for implement the slave (hardware) and the master > (software) for the 16C73 specifically. I'm using the library routines that came with my C compiler. I have heard others using the AN554 code. > Did anybody tried the code in the AN554 successfully? I am trying to > use it but unsuccessfully... What is the problem, specifically? > What is the value the pull up resistors should be? That depends. Smaller pull ups can pull the bus lines high faster when there high parasitic capacitance (like from long wires). But they use more power. I recommend starting with a guess on bus capacitance, choose the pull ups for your bus speed and supply voltage, then checking the rise times with an oscilloscope to make sure the rise times are OK. A typical example: for standard mode (100 kbps), 5V levels, and 100pF bus capacitance, you'll need 8 kOhms maximum. Faster speed or more parasitic capacitance will require smaller pullups. ------------ Barry King, KA1NLH Engineering Manager NRG Systems "Measuring the Wind's Energy" Hinesburg, Vermont, USA barry@nrgsystems.com "The witty saying has been deleted due to limited EPROM space"