Siemens SIMATIC ET 200AL, System Manual

Page: 1224 / 2255

Communications services
3.6 Secure Communication
Communication
Function Manual, 05/2021, A5E03735815-AJ
103
PG/HMI and CPU connected differently
As explained in the previous sections, the secure PG/HMI connection as of V17 between the
PG/HMI device and CPU (current version) is characterized by the employed standardized
communication procedure, TLS (Transport Layer Security).
You have the option of connecting a V2.9 CPU to a current programming device with TIA
Portal V17 or higher and additionally, for example, to an HMI device with a runtime from the
previous version: The devices automatically adjust their connection mechanisms accordingly.
In order to be able to better differentiate between the two connection mechanisms, we call
the previous procedure, which is based on a variant of S7 communication, "Legacy
procedure" for short.
In summary ("PG" here stands for a programming device with TIA Portal):
•
PG/HMI and CPU come with the V17 (or subsequent version): TLS procedure is used.
• PG/HMI comes from a predecessor version (< V17): Legacy procedure is used - provided
that you have deactivated the option "Only allow secure PG/PC and HMI communication"
in the CPU properties.
• CPU comes with V17 (or higher), several PGs/HMIs are connected and come from both
V17 (or higher) and previous versions: TLS + legacy procedures are used - provided that
you have deactivated the option "Only allow secure PG/PC and HMI communication" in the
CPU properties.
When the CPU state changes
The diagnostics buffer provides you with information if its status changes due to events in
connection with the Secure PG/HMI Communication.
Examples:
•
After successfully loading a configuration with a configured password, the diagnostics
buffer reports that the CPU is changing from the provisioning phase to Secure Mode (TLS
procedure).
• You have connected a PG with TIA Portal V17 to a CPU V2.9. Secure PG/HMI
communication (TLS procedure) is established automatically.