I am having problems communicating between a CP1E-N30 PLC and NB7W HMI.
They are connected via an RS-232 cable from the built-in COM0 port of the PLC to COM1 on the HMI.
When I first connected them I got the message “PLC No Response 00-00-1” on the HMI. After checking all the settings at both ends and restarting the PLC & HMI a couple of times, the communications suddenly started working correctly. I’m not sure what I did to make this happen.
Recently I moved my programs to a new PLC (another CP1E-N30) and now I’m back to the old problem of “PLC No Response …”.
On investigating further I find the HMI is sending a data pulse to the PLC every 2 sec. or so (LED flashes on the RS-232 port of the PLC) but there is nothing back from the PLC. Also A392 in the PLC has a value of &16, A392.04 is set to 1. From the software manual, this is “ON when an error has occurred at the built-in RS-232C port.” I’ve tried clearing A392.04, but it is immediately set again. Also I’ve tried using COM2 on the HMI, but the result is the same, so the problem would appear to be at the PLC end.
Any suggestions on a reason for this problem? I thought I had copied all the settings from the old PLC to the new one (matching baud rates, etc.), but is there something I could have missed causing the comms problem? I am using HostLink protocol as this worked on the old PLC. The manuals are a bit unclear on protocols, in one place saying to use 1:N NT Link protocol, and in another saying this doesn't work with the NB.
