Freescale Semiconductor MPC5553 - Loop Operation

MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
21-32 Freescale Semiconductor
21.4.7 Loop Operation
In loop operation the transmitter output goes to the receiver input. The RXD signal is disconnected from
the eSCI.
Figure 21-22. Loop Operation (LOOPS = 1, RSRC = 0)
Enable loop operation by setting the LOOPS bit and clearing the RSRC bit in eSCI control register 1
(ESCIx_CR1). Setting the LOOPS bit disables the path from the RXD signal to the receiver. Clearing the
RSRC bit connects the transmitter output to the receiver input. Both the transmitter and receiver must be
enabled (TE = 1 and RE = 1).
21.4.8 Modes of Operation
21.4.8.1 Run Mode
This is the normal mode of operation.
NOTE
The eSCI does not support a freeze mode. If the device is being operated in
debug mode, the eSCI will continue to shift data if the e200z6 core asserts
a freeze.
21.4.8.2 Disabling the eSCI
The module disable bit (ESCIx_CR2[MDIS]) in the eSCI control register 2 can be used to turn off the
eSCI. This will save power by stopping the eSCI core from being clocked.By default the eSCI is enabled
(ESCIx_CR2[MDIS]=0).
Transmitter
Receiver
TXD
TXD Output Signal
RXD