This diagram is intended to illustrate loopback paths and therefore may omit some normal-mode paths.
tr
Reeeeeeeeee
TX
RX
TX SHIFT REG
RX SHIFT REG
Checks the analog loopback path through the transmit buffer
Checks the analog loopback path through the receive buffer
Digital loopback path
RXP_ENA
LPBK_TYPE
Basic Operation
1532
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
Multi-Buffered Serial Peripheral Interface Module (MibSPI) with Parallel Pin
Option (MibSPIP)
Figure 28-31. I/O Paths During I/O Loopback Modes
28.2.10.2.1 Input/Output Loopback Mode Operation in Slave Mode
In multi-buffer slave mode, there are some additional requirements for using I/O loopback mode (IOLPBK).
In multi-buffer slave mode, the chip-select pins are the triggers for various TGs. Enabling the IOLPBK
mode by writing 0xA to the IOLPBTSTENA bits of the IOLPBKTSTCR register triggers TG0 by driving
SPICS to 0. The actual number of chip selects can be programmed to have any or all of the SPICS pins
as functional. All other configurations should be completed before enabling the IOLPBK mode in multi-
buffer slave mode since it triggers TG0.
After the first buffer transfer is completed, the CSNR field of the current buffer is used to trigger the next
buffer. So, if multiple TGs are desired to be tested, then the CSNR field of the final buffer in each TG
should hold the number of the next TG to be triggered. As long as TG boundaries are well defined and are
enabled, the completion of one TG will trigger the next TG.
To stop the transfer in multi-buffer slave mode in I/O Loopback configuration, either IOLPBK mode can be
disabled by writing 0x5 to the IOLPBTSTENA bits or all of the TGs can be disabled.