Dear Sir,

Regarding the subject, J1939 Termination Resistor can be checked or unchecked in System Settings. Please find attached. Please let me know how this function is.

Best regards,
Shiii

Dear Shiii-san,
On high speed serial communication channels (such as Video channels or Mil-STD-1553 or the CAN Bus where you have multiple devices connected) you typically need to terminate the bus to prevent ringing or reflection of the signal on the bus. The CAN bus is no different and it needs a 120 ohm resistor in parallel (between the High and Low signal lines) at typically the last device on the bus. Most devices, such as Engine Control Units, do not provide the termination or it may be incorporated in the cable or better yet the termination is provided in the software configuration of the display.

It has been our experience that absolutely no termination is very bad for communication. You will see missed and corrupted messages. If you have some other device which is terminated, communication should be good. If you have extra devices provide termination, the communication should continue to be good. If your are not sure about whether the bus is terminated or not, set the Display configuration to include termination even if you have multiple displays running the same Configuration file. We have not seen an issue with too much termination.
Thanks,
Phil Cebuhar

Dear Phil-san,

Thank you for your attention and explanation.

If I check the box of "Enable CAN1" on the system settings, termination is provided and no other termination resistors do not need to be added in the CANbus line. Is my understanding correct? Before and after I checked the "Enable CAN1", I measured actual resistance values in the CANbus line connected with the PV750, but there was any difference between the measured values.

Best regards,
Shiii

Dear Shiii,

I believe a power cycle is required when enabling/disabling the terminating resistor via software. Try a power cycle and then measure across the CAN high and low terminals.

-Jacob