M3 GPIO Mux
C28 GPIO Mux
M3
U
A
R
T
4
P
e
ri
p
h
e
ra
l
C28
S
C
I‐
A
P
e
rip
h
e
ra
l
SERPLOOP[UART4TOSCIA]
0
1
0
1
Tx
Rx
Rx
Tx
C28 SCI-A to M3 UART4 Internal Loopback
1030
SPRUHE8E – October 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
C28 Serial Communications Interface (SCI)
illustrates the loopback connections between the C28 SCI-A and M3 UART4. The C28 SCI-
ATx is connected to the M3 UART4Rx and C28 SCI-ARx is connected to M3 UART4Tx when loopback
mode is enabled. Loopback is enabled by setting the UART4TOSCIA bit in the M3 SERPLOOP register.
For a complete description of the SERPLOOP register, refer to the
System Control and Interrupt
chapter.
Figure 13-11. UART and SCI Connections for Loopback Mode
13.2.1 Loopback Initialization and Configuration
To enable M3 UART4 to C28 SCI-A loopback, follow these steps:
1. Enable and configure the M3 UART4 module by following the steps outlined in the Initialization and
Configuration section of the
M3 Universal Asynchronous Receivers/Transmitters (UARTs)
chapter.
2. Enable internal loopback mode by setting SERPLOOP[UART4TOSCIA] = 1 on the M3 subsystem.
3. Enable and configure the C28 SCI-A module as described in
.
To disable loopback between the M3 and C28, set SERPLOOP[UART4TOSCIA] = 0.