Under what circumstances would the XBEE S2C Issue a serial break?

We are seeing some issues where an XBEE S2c that is driven by a PIC18F where the Serial port starts to show OK over and over.

we can see a serial break (serial lines go low) and then the OK about every 2 sec. We thought that the RESET line on the XBEE is being toggled by the PIC, but those lines are stable when viewed on an scope…

We can see the serial break via a logic analyzer trace…

  • Power is stable over the entire session at Vcc of the radio
  • the reset line on the radio is stable over the entire time
  • the PIC18F is NOT resetting via watchdog or other, we can see this via toggled output from the pic.
  • only the xbee is doing this

So what could cause this?

This would occur if the Data in line was held low as well on power up.