The CAN-Transceiver TJA1051 can be set into "silent Mode".
A HIGH level on pin S selects Silent mode -> the transmitter is disabled -> releasing the bus pins to recessive state.
According to Application Hint AH1014 - Rev.01.40 - 27 April 2015:
"Chapter 3.3.2 Bus dominant clamping prevention at entering Normal Mode
Before transmitting the first dominant bit to the bus in Normal Mode the TXD pin once
needs to be set HIGH in order to prevent a transceiver initially clamping the entire bus
when starting up with not well defined TXD port setting of the microcontroller."
Now my question:
How low do I have to wait from setting pin S to LOW (leaving silent mode > entering normal mode), till I can send a dominant Bit?
Thanks for your effort and your respones
The intention is to avoid TXD dominant time out when TXD was set to dominant for long time 0.5ms to 5ms.
So, if counter for TXD dominant time out was reset by setting TXD to recessive once, the dominant time out doesn’t happen after entering Normal mode.
Time for keeping TXD in Recessive is not so critical.
So, while silent mode is selected by S=High, TXD should be set to Recessive.
Dominant can be selected after S is set to Low.
Please see below the answer I received on this from our expert:
The longest mode change time is less than 50 µs. Thus it is recommended to wait these 50 µs to ensure a proper functionality. Note that after entering Normal mode and before starting transmission of the first dominant bit (start of frame) the TXD pin shall be recessive (TXD = HIGH).