• State TI Thinks Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 2 answers
  • Subscribers 34 subscribers
  • Views 2205 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.

MAX3227E: When loopback the IC not working

user4764564
Intellectual 380 points
Part Number: MAX3227E


Hi, When i loopback RS232_Tx and RS232_Rx, it doesnot produce any output. Below is my schematic TX, RX are connected to UART cable. Please give some application or testing circuit.

  • 0
    TI__Guru 62920 points

    Hello,

    To confirm - you are connecting pin 8 to pin 13, correct?  Can you please show us the waveforms on pins 11, 8, and 9 so that we can see what might be going wrong?  Does the device work well under normal conditions (not loopback)?

    Regards,
    Max

  • 0 in reply to Miguel Robertson
    Intellectual 380 points

    Thanks for your reply. My circuit did not work well in normal condition so, i tried to test the IC by loopback it. When I checked the wave form in 8th pin, there comes square wave whereas in 9th pin i got an inverted square waveform of 8th pin. But i received nothing from 13th and 11th pins.

  • 0 in reply to user4764564
    TI__Guru 62920 points

    Which pins are connected to which in your loopback test?  Pin 8 is an RS-232 input, and you should see an inverted version of its data pattern on the logic-level pin 9 output.  Pin 11 is a logic-level input, and you should see an inverted version of its data pattern on the pin 13 RS-232 output.  So, you should either apply a waveform to pins 8 or 11 and should connect a loop-back wire either from pin 13 to 8 or from pin 9 to 11.  If you are doing this and seeing issues, please send us the signal waveform captures so that we can verify the signal properties are all within the specified ranges for the device.

    Regards,
    Max

  • 0 in reply to Miguel Robertson
    TI__Guru 62920 points

    Hello,

    Have you been able to resolve this issue?  Or, do you have any updates you can share with us?

    Thank you,
    Max

  • 0 in reply to Miguel Robertson
    Expert 1120 points

    Hi Robertson,

    We are able to loopback the data, but when data is provided through rs-232 for loopback most of the data gets dropped and only a fewer data got return back

  • 0 in reply to sasi kumar1
    TI__Guru 62920 points

    It looks like the last character typically makes it through the loopback.  Based on this, I think it is much more likely that this behavior is related to the serial port implementation than the transceiver/PHY.  (A physical layer issue would typically give junk data or result in a data line that is stuck high or low.)  You can confirm this by checking the TX and RX waveforms on an oscilloscope during the test.

    Max