SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
The MCAN_TEST register write access is enabled by setting the test mode enable MCAN_CCCR[7] TEST bit to 1. The MCAN_TEST register allows the configuration of the test modes and test functions.
The CAN transmit MCAN_TX pin has four output functions. One of those functions can be selected by programming the MCAN_TEST[6:5] TX filed. Additionally to its default function (the serial data output) it can drive the CAN Sample Point signal to monitor the MCAN's bit timing and it can drive constant dominant or recessive values.
The actual value of the CAN receive MCAN_RX pin can be monitored from MCAN_TEST[7] RX bit. Both functions can be used to check the CAN bus physical layer. Due to the synchronization mechanism between CAN clock (MCAN_FCLK) and Host clock (MCAN_ICLK) domain, there may be a delay of several Host clock periods between writing to the MCAN_TEST[6:5] TX filed until the new configuration is visible at the output MCAN_TX pin. This applies also when reading input MCAN_RX pin via the MCAN_TEST[7] RX bit.
Test modes should be used for self test only. The software control for MCAN_TX pin interferes with all CAN protocol functions. It is not recommended to use test modes for application.