Chapter 13. Physical Layer Interface Controller (PLIC)
13-21
PLIC Registers
13.5.8 Loopback Control Register (PLCR)
All bits in this register are cleared on hardware or software reset.
The PLCR is an 8-bit register containing the configuration information for all four ports on
the MCF5272.
11
M/S
Master/Slave. Defines the direction of the DCL1 and FSC1 pins.
0 DCL1 and FSC1 are inputs and are sourced from an external master. Note: This bit is relevant to
port 1 only, as port 0 is always in slave mode.
1 enables DCL1 and FSC1 to be outputs, that is, the MCF5272 drives DCL1 and FSC1.
10
G/S
GCI/SCIT.
0 The normal mode of GCI is used (i.e. no D-channel contention control).
1 Selects SCIT mode of operation for the GCI interfaces.
9
FSM
Frame Sync Master.
0 Default reset value. 2-KHz interrupt is generated from port 0.
1 Port 1 FSC/FSR is used to generate the 2-KHz interrupt.
8
ACT
GCI Activation.
0 Default reset value.
1 Causes Dout to transition to a logic low for the respective port. This bit is only operational when
the port is in GCI mode. Setting the ACT bit in any other mode has no effect. It is the responsibility
of the CPU to clear the ACT bit when normal operation on Dout is required. This bit is intended to
be used to request activation from the upstream DCL/FSC driver. Periodic interrupts commence as
soon as the upstream device generates DCL, provided the appropriate interrupts, such as IE,
B1RIE, and so on, are enabled for the port.
7
DMX
Data multiplex.
0 port 3 Dout and Din are multiplexed onto Dout1 and Din1.
1 enables port 3 Dout and Din to be connected to dedicated output and input pins, DOUT3 and
DIN3.
3
SHB2
B2 channel shift direction.
0 B2 channel data is received/transmitted msb first. The msb-first convention is often used for
communication with PCM CODECs and converters.
1 B2 channel data is received/transmitted lsb first. The lsb-first convention is used when the data is
to be HDLC encoded.
2
SHB1
B1 channel shift direction. See SHB2.
1
ENB2
Enable B2 data channel.
0 The B2 channel is disabled and all periodic interrupts in both receive and transmit directions are
disabled. The behavior of Din and Dout in this state is shown below.
1 Enables the B2 data channel for the respective port.
0
ENB1
Enable B1 data channel. See ENB2.
Table 13-2. P0CR–P3CR Field Descriptions (Continued)
Bits
Name
Description
Mode
Din
Dout
IDL
All 1s
High Impedance
GCI
Operational (data on
Din visible)
Open drain
Содержание DigitalDNA ColdFire MCF5272
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