Communication Lag between M172 PLC and TM172DCLxxx HMI Display

[Waqasz]

How do we manage lag of communication between TM172DCLxxx HMI displays and TM172 PLC especially during TM172 PLC reboot. As TM172 PLC takes some time to reboot and during that time TM172DCLxxx HMI show numerical values as 0 which can create problems and in some cases they get written to PLC variables as scan is restored between them. How do we manage this behaviour ? In EOTE/ST6, there are some option(s) to manage external behaviour, HMIST6xxx either display last known values or does not load screens at all until communication scan is restored between HMI and PLC . 

[FedericoM · Accepted solution]

Hello,

ESME HVAC hasn't this kind of feature.

Here attached a project which shows how I manage the communication between TM172DCL and TM172P.

Communication status is managed in the Programming part, program ModbusComWithSlave.

In this program all the R/W managed by Display part are enabled/disabled based on the communication status using sysMbMRtuNodePresence[].