hi,

The communication port must be bidirectional, its output is open-drain, and there is a weak pull-up on the line.

For 1-wire, just consider ports 1...3 as P0+weak pullup (implemented internally).

Note as well that some 1-Wire devices (for example, DS1920) require strong pull-up for some operations. In this case one more pin + external transistor are used usually.

Regards,
Oleg