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Communication between MAX3243 and SN75C1406

Ronak Desai
Intellectual 545 points

Other Parts Discussed in Thread: MAX3243, SN75C1406

Hi,


We are facing a problem in our designed custom board. On our board we are using MAX3243 Transceiver for Serial communication and it works fine.


But, now we came across serial communication problem with another custom board which has SN75C1406 Transceiver. It appears that there is some problem with the driving strength of signal.


Please refer the attached snapshot. Channel 1 is the actual signals that needs to be transmitted to the board having SN75C1406 chip. Now, as it is seen in the snapshot (Channel 2 waveform), when our board's MAX3243 tries to send data to SN75C1406 the signal level gets increases as well as it get distorted and because of that communication fails.


We though it's a problem with the drive strength of the charge pumps on our board, we increased that also but still we see the same behavior.

Please suggest what we can do to overcome/solve this problem.


Thanks,

RD

  • 0
    TI__Guru**** 171466 points

    Ronak,

    The SN75C1406 receiver input is a normal RS232 load and the MAX3243 should have no problem driving it.
    Is it possible the the MAX3243 output is connected to the SN75C1406 driver output by mistake?
    Are the grounds of both systems connected and at same voltage potential?

  • 0 in reply to Ron Michallick
    Intellectual 545 points

    Hi Ron,


    Thanks for the quick reply.


    We are taking power for our board from the same supply as the custom board uses which has SN75C1406, so by that way we are confirming that the both have common ground.


    Also, we are using standard serial cable between our board and the other board for communication, so we don't think that it has some cross connection, would you please suggest a method to confirm this.


    The snapshot I have attached in above post is for the data we transmit to the another board having SN75C1406, but I captured the signals when that other board sends to us.
     On our board we are able to receive the signals without distortion but has higher voltage levels, distortion problem is there only when we transmit to that board (Tx of MAX3243).

    Thanks,

    RD

  • 0 in reply to Ronak Desai
    TI__Guru**** 171466 points

    Ronak,

    Am I correct that data from the remote system is received correctly?
    I can not determine the cause for the incorrect driver output.
    I need more clues.


  • 0 in reply to Ron Michallick
    Intellectual 545 points

    Hi Ron,


    I have checked the connections in following way. I have connected the serial cable on the port of having SN75C1406N.  Then I checked continuity between pins of the SN75C1406N on the mother board and the pin out of the male connector on other side of the cable and following is the mapping.

    Pin-2 of male connector of cable ---> Pin-2 (1RA) on SN75C1406
    Pin-3 of male connector of cable ---> Pin-3 (1DY) on SN75C1406
    Pin-5 of male connector of cable ---> Pin-9 (GND) on SN75C1406


    Thanks,

    RD

  • 0 in reply to Ronak Desai
    Intellectual 545 points

    Just to confirm, we are connecting female to male straight serial cable to the board having SN75C1406N. Female connector gets connected on this board and male connector end goes into our board.


    Thanks,

    RD

  • 0 in reply to Ronak Desai
    TI__Guru**** 171466 points

    Ronak,

    Pin-2 of male connector of cable ---> Pin-2 (1RA) on SN75C1406  (also MAX3243 DOUT?)
    Pin-3 of male connector of cable ---> Pin-3 (1DY) on SN75C1406  (also MAX3243 RIN?)
    Pin-5 of male connector of cable ---> Pin-9 (GND) on SN75C1406

    Do the wave forms on MAX3243's, VCC, V+ and V- look good?

  • 0 in reply to Ron Michallick
    Intellectual 545 points

    We have identified the problem.


    MAX3243 is a pure RS232 transceiver while SN75C1406 is not, and thus unused pin except the required pins (2,3,5) were causing this problem. If we connect only these 3 pins between MAX3243 and SN75C1406 then everything works fine.

    -Ronak