Motorola MPC860 PowerQUICC, User Manual

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MOTOROLA Chapter 34. Parallel I/O Ports 34-1
Chapter 34
Parallel I/O Ports
340
340
The CPM supports four general-purpose I/O portsÑA, B, C, and D. Each signal in the I/O
ports can be conÞgured 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 SCC[1Ð2] (and SCC[3Ð4] for
Rev. B and later), the bank of clock signals, and some time-division multiplexed
(TDM) signals.
¥ Port B is shared with the parallel interface port (PIP) and other functions such as
TDM, IDMA, SMC, SPI, and I
2
C signals.
¥ Port C is shared with the RTS, CTS, and CD signals of the SCCs as well as some
TDM signals. However, port C is unique in that its signals can generate interrupts to
the CPM interrupt controller (CPIC).
¥ Port D is shared with the RXD and TXD signals of SCC[3Ð4], TDM signals, and
Ethernet CAM-support signals.
The read/write port signals can be conÞgured as inputs or outputs with a latch for data
output. They can be conÞgured to be either general-purpose I/O or dedicated peripheral
signals. Regardless of the programmed function, the I/O signalsÕ state can always be read
from their data registers (PxDAT).
Ports A and B have signals that can be conÞgured 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 ßexible conÞguration of the CPM, many dedicated peripheral functions are
multiplexed onto ports A, B, C, and D. Functions are grouped to maximize the signalsÕ
usefulness to the greatest number of MPC860 applications. To understand signal
assignments described in this chapter, it helps to understand each CPM peripheral.