Not too much information given, but, the go-to would be SERIAL, 'DF1' protocol, since that pretty much always works.
Of course, depending on which PLC5 you have, you may have other options - as a field bus slave, etc.
And, of course, depending on which EZ Panel you choose, that may limit those options.
We figured it out yesterday afternoon we used an AIC module and had to make our own 25 pin serial connector and 9 pin serial connector also .. Thank you for responding