In TJA1145 is not sleeping it is in standby

[payyanr]

In TJA1145 , the CWE bit (Reg add 0x23) is getting resetted. What are the precondition to set the bit. SW is sending 0x4601 to set the bit.But in the next millisecond , when the register is read again, it shows that the bit is resetted. Please help.

[TomasVaverka]

Hi Payyan,

The CWE bit could be set before entering to Standby/Sleep mode if remote wake up is needed.
Register bits may change automatically when TJA1145 switches from one mode to another. Table 31 of the datasheet summarizes this (https://www.nxp.com/docs/en/data-sheet/TJA1145.pdf).
The CWE you mentioned is cleared in the OFF mode (upon power up), then no change is done between modes, unless the TJA1145 is forces to enter Sleep mode (du to Vcc or Vio undervoltage detection). In this case the CWE bit is set. Note if an SPI transmission is in progress when the TJA1145 changes state, the transmission is ignored (automatic state changes have priority).
Further details of the TJA1145 behavior can be found in Application Hints document:

https://www.nxp.com/docs/en/supporting-information/AH1309_v1_1_Application_Hints_TJA1145.pdf

Best regards,

Tomas

[payyanr]

Hello Tomas,

Thanks for your support and comment.

In our case, the CWE bit is set with the command 0x4601.This is ensured by reading it again in the next milli second.

But when we read it again in the very next time with 0x4700, the reply is 0x4700.  So the bit is cleared.

So when we send the sleep command (0x201), the Transceiver is going to standby.

The statement "SPI transmission is in progress when the TJA1145 changes state, the transmission is ignored " is for

Normal/standby/sleep state change request right ?

Another observation we made was when the transceiver is in Normal (MC =0x7), the CMC toggles between 00(offline) to 01(active). What could be the reason for the toggle ?

We checked all the voltage (batt,VCC,VIO) everything is OK.

[ramyavinod]

Hello!

I have the same problem,I can't transit  the TJA1145 to enter the sleep mode.

Clearing the event status register yields no success.

System event status register (address 61h), PO bit is always 1 , and I set 1 to clear isn't useful.

So cannot transit TJA1145 to sleep mode. 

Please do help me .

Note:

With arduino same implementation works successfully but not with Attiny.

[payyanr]

Hello Ramya,

Did you checked the BAT (Pin 10) of the TJA1145 with oscilloscope ? is there any toggling ?

[ramyavinod]

Hello,
Yes i tried everything seems to be ok only System status register (address 0x61) is not getting clear.