Port B is an 8-bit bidirectional I/O port with internal pull-up resistors (selected for each
bit). The Port B output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port B pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset
condition becomes active, even if the clock is not running.
Port B also serves the functions of various special features of the ATmega16 as listed
on page 58.
You want this to be translated? Or the functions listed on page 58?
Ok, I'll try to translate this and maybe later the functions.
The first sentence states that Port B is basically an 8 bit or 1 byte port that can be set as input or output. It also state that it has internal pull-up resistors selectable for all or each bit (pin).
The second sentence states that used as output, Port B has buffers that can source (provide current, like connecting something to power) or sink (absorb current, like connecting something to ground).
The third sentence warns you that when used as input, Port B pins that are connected externally to the ground (directly or through a resistor) and have the internal pull-up resistor activated will have a current going towards the ground (directly or through the resistor). This is a waste of power, bad for a robot.
The fourth sentence states that Port B pins will be disconnected from the circuit (state Z, high impedance) when the reset pin will be triggered (usually pulled low - connected to the ground). More about tri-state on the link below:http://www.cs.umd.edu/class/spring2003/cmsc311/Notes/CompOrg/tristate.html
Does this help?