Parallel I/O Ports
MPC885 PowerQUICC Family Reference Manual, Rev. 2
34-12
Freescale Semiconductor
PCDIR and PCPAR bits are cleared at system reset, making all port signals general-purpose inputs. The
CPM interrupt mask register (CIMR) (see
Section 35.5.3, “CPM Interrupt Mask Register”
) is also cleared,
so port C I/O signals left floating do not cause false interrupts.
General-purpose port C I/O signals can be accessed through PCDAT where written data is stored in an
output latch. If a port C signal is configured as an output, output latch data is gated onto the port signal.
Reading PCDAT reads the value of the port signal itself. For port C input signals, data written to PCDAT
is stored in the output latch but cannot reach the port signal. In this case, when the PCDAT register is read,
the state of the port signal is read.
The following steps configure port C signals as general-purpose outputs. When the signal is configured as
an output, port C interrupts are not generated.
1. Write the corresponding PCPAR bit with a 0.
2. Write the corresponding PCDIR bit with a 1.
3. Write the corresponding PCSO bit with a zero (for clarity).
4. The corresponding PCINT bit is a ‘don’t care.’
Table 34-11. Port C Pin Assignment
Signals
PCPAR[DD
n] = 0
PCPAR[DD
n] = 1
Input to On-Chip
Peripherals
(Default)
PCDIR[DR
n] = 1
or PCSO[
n] = 0
PCDIR[DR
n] = 0
and PCSO[
n] = 1
PCDIR[DR
n] = 0 PCDIR[DRn] = 1
PC15
Port C15
DREQ0
RTS3
RxCLAV
1
TxCLAV
2
1
PDPAR[UT] = 1 and UTMODE[RSL] = 0, see
Section 42.2.3, “Port C—MasterRxClav/Slave TxClav Signal.”
2
PDPAR[UT] = 1 and UTMODE[RSL,SPLIT] = 0b11, see
Section 42.2.3, “Port C—MasterRxClav/Slave TxClav
Signal.”
L1ST1
DREQ0 = V
DD
PC14
Port C14
DREQ1
RTS2
L1ST2
DREQ1 = V
DD
PC13
Port C13
—
MII1-TXD3
SDACK1
—
PC12
Port C12
—
MII-TXD2
TOUT1
—
PC11
Port C11
USBRXP
—
GND
PC10
Port C10
USBRXN
TGATE1
GND
PC9
Port C9
CTS2
—
GND
PC8
Port C8
CD2
TGATE2
GND
PC7
Port C7
CTS4
L1TSYNCB
USBTXP
CTS4 = GND
L1TSYNCB = PD13
PC6
Port C6
CD4
L1RSYNCB
USBTXN
CD4 = GND
L1RSYNCB = PD12
PC5
Port C5
CTS3
L1TSYNCA
SDACK2
CTS3 = GND
L1TSYNCA = PD15
PC4
Port C4
CD3
L1RSYNCA
CD3 = GND
L1RSYNCA = PD14
Summary of Contents for PowerQUICC MPC870
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