We are using the TJA1100 as a PHY with MPC5746C.
I need to check the cable errors during the run time, either for open/short circuit between the twisted pair cables.
So I actually tried to shorten the two wires or unplug the cable from the Trcv connector and indeed I got the Link-fail counter interrupt which is fired due to the high losses/noisy channel and inside this interrupt ISR I'm gonna run the cable diagnostics, But I have some inquires
1 - If an open or short circuit happened, shall this forces the Trcv chip to go to Power down mode or it will stay in the power up mode ?
2 - Is there a specific procedure to check the cable errors " shall I write some bits in any registers " ?
according to the cabling errors section, shall I put the controller in power down mode to disable all communications ?
and then set the cable test bit, then reset the Trcv in power up as it was ?
3 - I have a very weird observation: while the controller is communicating by debugging I found that the POWER_DOWN bit in the Basic control register (Register 0) equals 1, and as stated in the datasheet 1 means Trcv is in power down.
meanwhile the POWER_MODE bits(14:11) in the Extended control register (Register 17) give the value 0011 which means normal mode, so what is wrong here ?
4 - Also when I shorten the two twisted wires or unplugged them and read the External status register (Register 25)
and check on bit 7&8, I found that it didn't indicate any problem, I mean it is saying that there is no cable errors while I'm forcing a shorten or opening to the wires.