Motorola MPC8260 - Manual (Page 957)

MOTOROLA Chapter 35. Parallel I/O Ports 35-1
Chapter 35
Parallel I/O Ports
350
350
The CPM supports four general-purpose I/O portsÑports A, B, C, and D. Each pin in the
I/O ports can be conÞgured as a general-purpose I/O signal or as a dedicated peripheral
interface signal. Port C is unique in that 16 of its pins can generate interrupts to the interrupt
controller.
Each pin can be conÞgured as an input or output and has a latch for data output, read or
written at any time, and conÞgured as general-purpose I/O or a dedicated peripheral pin.
Part of the pins can be conÞgured as open-drain (the pin can be conÞgured in a wired-OR
conÞguration on the board). The pin drives a zero voltage but three-states when driving a
high voltage.
Note that port pins do not have internal pull-up resistors. Due to the CPMÕs signiÞcant
ßexibility, many dedicated peripheral functions are multiplexed onto the ports. The
functions are grouped to maximize the pinsÕ usefulness in the greatest number of MPC8260
applications. The reader may not obtain a full understanding of the pin assignment
capability described in this chapter without understanding the CPM peripherals.
35.1 Features
The following is a list of the parallel I/O portsÕ important features:
¥ Port A is 32 bits
¥ Port B is 28 bits
¥ Port C is 32 bits
¥ Port D is 28 bits
¥ All ports are bidirectional
¥ All ports have alternate on-chip peripheral functions
¥ All ports are three-stated at system reset
¥ All pin values can be read while the pin is connected to an on-chip peripheral
¥ Open-drain capability on some pins
¥ Port C offers 16 interrupt input pins