• State TI Thinks Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 2 answers
  • Subscribers 34 subscribers
  • Views 437 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TCAN1145-Q1: The value of the real register cannot be read (that is, the second byte is always 0)

Alan Xia
Genius 9650 points
Part Number: TCAN1145-Q1

Hi team,

The customer uses the TCAN1145 chip. After powering on, the MCU sends a read 10h register instruction to TCAN1145. The value of the first byte 50h register returned by 1145 is 0xE0, and the second byte value is 0. The same goes for reading other registers (51h, 52h, etc.). Please help me find out why the real register value cannot be read (that is, the second byte is always 0), thank you

Note: SPI setting CPOL: 0 CPHA: 0 The rate is less than 4M
The attachment is an intercepted waveform picture. The line sequence from top to bottom is CS CLK SDO SDI (MCU side).

  • 0
    TI__Guru 53555 points

    Hi Alan,

    The address that appears on the SDI line does not look to be valid. There are three consecutive 1s in a row which is not indicative of the 50h address (0x5 is 0b0101). Including the shift for the read/write bit, it looks like the transceiver would recognise an attempt to read the register 0x70. This is a reserved address so the device simply returns all 0s for its contents.

     

    Please review the software that is used to generate this pattern and ensure the correct shifting is done to the register bits and the right address value is being used here. 

    Let me know if you have any more questions. 

    Regards, 
    Eric Schott 

  • 0 in reply to Eric Schott1
    Prodigy 140 points

    Hi Eric Schott 

    Thank you for your help.The SDO identified in the figure is the output of MCU SPI, and SDI is the input of MCU SPI. MCU sends an instruction 0x20 0x00 to TCAN to read the 0x10 register, while TACAN replies with 0xE0 0x00. I understand that reading 0x10 is a normal register address. So please help confirm again,thanks.

    Regards

  • 0 in reply to Yanni Ying
    TI__Guru 53555 points

    Hi Yanni,

    Thanks for correcting the signals here. It is clear that the MCU has formatted this read correctly. 

    Can you confirm that the INH signal is high during this test to show that the transceiver is not in sleep mode? There are some extra timing requirements for the SPI if the transceiver is in this mode. Note it is possible for the device to automatically enter sleep mode after ~4 minutes from powering on. 

    Do SPI writes appear to have any impact on device behavior? Does writing to the mode control register impact the state of the INH signal for instance if the device is placed into or out of sleep mode? 

    Regards, 
    Eric Schott 

  • 0 in reply to Eric Schott1
    Prodigy 140 points

    Hi Eric Schott 

    Thank you for your help.We have replaced it with a new TCAN1145 chip, which makes SPI communication easy to use.

    But now we have encountered another problem. Set TCAN1145 to normal mode and read the 0x10 register to return a value of 0x07 (normal) There is no problem with the MCU receiving CAN messages. However, the CAN message cannot be sent out, and the waveform of the data being intercepted and sent is shown in the figure below (from top to bottom TXD RXD). The waveform of TXD is clearly chaotic. Please help confirm the reason for the abnormal TXD waveform. The CAN controller is functional and has undergone differential verification. Currently, the problem is mainly on the TCAN transceiver.Thank you.

    Regards

  • 0 in reply to Yanni Ying
    TI__Guru 53555 points

    Hi Yanni,

    I'm glad to hear replacing the device cleared up the first problem. 

    The TXD signal is an input signal to the transceiver. The TCAN1145 does not have any capability to drive this signal state apart from a constantly present weak pull-up bias. The multiple low levels on the signal in the scope shots make me suspect that there are two devices trying to drive this signal state simultaneously and we are seeing the resulting contention. 

    Do you know if any other device share the TXD signal trace besides the transceiver and the MCU? Sharing the schematic of the circuit may help us identify what could be causing this. 
    Please confirm that the correct pins are being probed here and that the RXD and TXD signals are connected correctly to the MCU. 
    For differential verification, this board has been able to send CAN data with another transceiver? Was there anything else different with the test setup for this verification than is present for the test with TCAN1145? 

    Regards,
    Eric Schott  

  • 0 in reply to Eric Schott1
    Prodigy 140 points

    Hi Eric Schott 

    Thank you for your help.It should be a hardware circuit issue.After the hardware colleagues completed the renovation, the can tx is ready to use.Thank you.

    Regards