Dixon,

I2C ports work find with any 8051 port. You wouldn't want to waste the RX & TX pins on I2C. The communications protocols are two different.

I usually place the two I2C lines on Port 0 which already requires resistor pullup lines to +5v. I2C requires a pullup on its DAT signal at least. Since it requires pullups and port 0 requires pullups, mapping the pins there is more efficient. However, if you are using external memory and need the Port 0 for that, you should move the I2C DAT and CLK off of Port 0.

The interface code you'll write or download and patch, will "bit-bang" the port CLK and DAT signals. This means that your program will deal with the protocol at a very primative level - it will control when a DAT or CLK go high and low and when DAT is used as an input or an output. There will be no higher level built-in advantages UNLESS you use a more expensive microprocessor with a featured I2C support.

Now, about the temperature sensor. The DS1820 was a good selection if you need accuaracy. Most simple temperature sensors are quoting +/- 2C accuracy. In my opinion that is too loose if humans are going to view the data particularly in countries that use degrees in Fahrenheit. The DS1820 was +/- 0.5C if I recall correctly.

I'll take a look at the DS1620 and DS1624 because I'd like a good, accurate temperature sensor for system monitoring.

-Jay C. Box

PS: You can find some I2C code examples on the Philips homepage (they champion the interface which they inherited when they bought out Signetics).

Peter probably also has some information on his homepage which he'll probably post if he sees your message.

Good luck.