mcf5272 Freescale Semiconductor, Inc, mcf5272 Datasheet - Page 305

• Manufacturer Part Number: mcf5272
• Description: Mcf5272 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

MOTOROLA
The loopback modes are independent signal loopbacks for the respective ports. These
loopbacks allow for the echoing of local or remote information. In auto-echo or
remote-loopback modes there is no time switching or time slot assignment function. All
data received on Din is transmitted on Dout during the same time slot. Similarly, in
local-loopback mode, the information transmitted on the Dout pin is echoed back on Din
during the same time slot.
The PLIC transmitter and receiver should both be disabled when switching between modes.
13.2.4.1 Automatic Echo Mode
The port automatically retransmits the received data on a bit-by-bit basis in this mode. The
local CPU-to-receiver communication continues normally, but the CPU-to-transmitter link
is disabled. While in this mode, received data is clocked on the receiver clock and
retransmitted on transmit Dout pin.
13.2.4.2 Local Loopback Mode
TxData is internally connected to RxData in this mode. This mode is useful for testing the
operation of a local port by sending data to the transmitter and checking data assembled by
the receiver. In this manner, correct channel operations can be assured. Also, both
transmitter and CPU-to-receiver communications continue normally in this mode. While in
this mode, the receive Din pin is ignored, the transmit Dout is held marking, and the
receiver is clocked by the transmitter clock.
13.2.4.3 Remote Loopback Mode
The channel automatically transmits received data on the transmit Dout pin on a bit-by-bit
basis in this mode. The local CPU-to-transmitter link is disabled. This mode is useful in
testing receiver and transmitter operation of a remote channel. While in this mode, the
receiver clock is used for the transmitter.
CPU
Disabled
(a) Automatic Echo
Rx
Tx
Chapter 13. Physical Layer Interface Controller (PLIC)
CPU
Disabled
Figure 13-9. GCI/IDL Loopback Mode
Disabled
Disabled
(c) Remote Loopback
Rx
Tx
Dout
Din
Disabled
Disabled
CPU
Din
Dout
(b) Local Loopback
Rx
Tx
Disabled
Disabled
GCI/IDL Block
Din
Dout
13-9