Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 919

Powerquicc family

Table of Contents

Parallel I/O Ports

The CPM supports five general-purpose I/O ports—A, B, C, D, and E. Each signal in the I/O ports can be

configured as a general-purpose I/O signal or as a signal dedicated to supporting communications devices,

such as SMCs and SCCs.

Port A is shared with the RXD and TXD signals of USB, SCC [2-4], some time-division

multiplexed (TDM) signals, and some of FEC1 signals.

Port B is shared with the parallel interface port (PIP) and other functions such as TDM, IDMA,

SMC, SPI, UTOPIA, and I

Port C is shared with the RTS, CTS, and CD signals of the SCCs as well as some TDM signals, and

FEC2 signals. However, port C is unique in that its signals can generate interrupts to the CPM

interrupt controller (CPIC).

Port D is for general-purpose I/O shared with SAR-specific RXD and TXD signals of SCC [3-4],

and TDM signals.

Port E is for general-purpose I/O shared with the signals used by the TDM, the MII and Reduced

MII interfaces, and SCC[3-4].

The read/write port signals can be configured as inputs or outputs with a latch for data output. They can

be configured to be either general-purpose I/O or dedicated peripheral signals. Regardless of the

programmed function, the I/O signals' state can always be read from their data registers (PxDAT).

Ports A,B, and E have signals that can be configured as open-drain. Open-drain signals drive a zero

voltage, but they three-state when driving a high voltage. Note that none of the port signals have internal

pull-up resistors.

To support flexible configuration of the CPM, many dedicated peripheral functions are multiplexed onto

ports A, B, C, D, and E. Functions are grouped to maximize the signals' usefulness to the greatest number

of MPC885 applications. To understand signal assignments described in this chapter, it helps to understand

each CPM peripheral.

Note that the FEC1-MII interface uses also I/O signals that are not part of the ports I/O:

Freescale Semiconductor

MPC885 PowerQUICC Family Reference Manual, Rev. 2