SPRUJF2A March 2026 – March 2026 AM13E23019
UNICOMM supports a multiple self-test modes which internally connect the output UNICOMM signals to the input UNICOMM signals. This mode is helpful for initial code development and debugging. There are two types of internal loopback modes in UNICOMM, internal loopback and inter-module internal loopback. Figure 22-2 shows an example of these two loopback setups with UNICOMM UART, as well as an external loopback hardware setup example.
Internal Loopback
For UNICOMM instances configured as UART or SPI, internal loopback within a single UNICOMM instance is available. The configuration for this mode is done in the UNICOMMUART_REGS and the UNICOMMSPI_REGS; see UART Internal Loopback and SPI Internal Loopback sections in the corresponding peripheral chapters.
Inter-Module Internal Loopback
Inter-module internal loopback is available between two different UNICOMM instances configured for the same communication type that are in the same SPG group. The Figure 22-1 shows which UC instances belong in each SPG grouping. In this loopback method, the following signals are connected between two different UC instances, represented as "i" and "j" below. Inter-module internal loopback is configured in the LPBKx.CONTROLLER and LPBKx.PERIPHERAL fields of the LPBKx registers. Then, enable the loopback pair by setting the EN bit in the LPBKx register. There is one configurable loopback pair available for each UNICOMM group on this device.
External Loopback
Additionally, users can configure any two UNICOMM instances in the UART IPMODE and connect the signals externally to validate the hardware setup. This requires no specific loopback configurations in any of the UNICOMM registers since the loopback is done external to the device.
UART