When I search this topic on the datasheet, I found that (picture), but I want to know that what is the voltage level on the tx and rx pins (I tested, and I see that is 5v to 0 V). Is there any information about this thing in datasheet or reference manual?
I haven't used that particular chip, but as I read it, Vddeh1 should be the supply voltage for the eSCI so the TX pin's high level should equal whatever you're feeding it on Vddeh1. The input voltage threshold for the RX line is probably given in terms of a fraction of the supply voltage, e.g. 0.7 x Vddeh1 or something. It's probably not specified for the RX function in particular - it'll be the same as any digital input.
Scott
Yes, that's correct. I will only add that the specification can be found in Table 22:
https://www.nxp.com/docs/en/data-sheet/MPC5634M.pdf
Search for VIL, VIH, VOL, VOH for the pads you need. In case of eSCI, it should be always slow pad - this can be found in Table 2.
Regards,
Lukas
Well, I was under impression that it's about MPC5634M but now I can see that the device is not specified in the question. But the answer will be similar anyway...