SPRUJ17H March 2022 – October 2024 AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1
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 TX pin has four output functions. One of those functions can be selected by programming the MCAN_TEST[6-5] TX field. 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 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 (FCLK) and Host clock (ICLK) domain, there may be a delay of several Host clock periods between writing to the MCAN_TEST[6-5] TX field until the new configuration is visible at the output TX pin. This applies also when reading input RX pin via the MCAN_TEST[7] RX bit.
Test modes should be used for self test only. The software control for TX pin interferes with all CAN protocol functions. It is not recommended to use test modes for application.