Srtp Server Operation In A Redundancy System - GE RX3i User Manual

Role Switching in Non-HSB Redundancy Systems
When redundant IP is enabled for an Ethernet module in a non-HSB CPU system, it is the responsibility of
application logic to set the redundancy mode of the Ethernet module. The Set Application Redundancy Mode
Service Request (SVC_REQ 55) instruction is used to inform the Ethernet module of the current redundancy role
of the host CPU. This SVC_REQ should be used to provide redundancy role switch notification to all Ethernet
interfaces in the controller that are configured for redundant IP operation.
After commanding a role switch for an Ethernet interface, the application logic can monitor the module's LAN
Interface Status (LIS) block to determine when it has activated the Redundancy IP address. For details about the
LIS, refer to "Monitoring the Ethernet Interface Status Bits" in Chapter 12
Note: The application must allow sufficient time for Redundant IP activation (at least 120msec) before
commanding another redundancy role switch.
When an Ethernet interface recognizes that a redundant IP address has been configured for it, the module
sends a mail message to the CPU to register for redundancy role switch notification. In non-HSB systems, the
Ethernet interface is initially put into backup mode. After power up, the application logic must use a SVC_REQ to
set the redundancy state to the desired value. Once running, the CPU remembers the last commanded
redundancy role sent to that Ethernet interface. When an Ethernet interface is restarted, the CPU automatically
commands the Ethernet interface to its last redundancy state without explicit action by the application logic.
Going to Stop Mode
When a non-HSB CPU goes to Stop mode, Ethernet interfaces that are configured for redundant IP are
automatically set to backup mode. When the CPU is subsequently returned to Run mode, the Ethernet interfaces
remain in backup mode until the application logic sets the redundancy mode to active.
Stop/IO Scan Enabled Mode
In this mode, I/O scanning including EGD service continues when the non-HSB CPU is stopped. However,
Ethernet interfaces configured for redundant IP operation are automatically set to backup mode and normal
EGD production for those interfaces is stopped. Only the EGD exchanges with Produce in backup mode enabled
are produced while the CPU is in Stop/IO Scan Enabled mode. To stop production for all EGD produced
exchanges including Produce in backup mode exchanges, choose the Stop/IO Scan Disabled mode of operation.
Commanding a Role Switch in a Non-HSB Redundancy System
Use the Set Application Redundancy Mode service request (SVC_REQ 55) with non-HSB CPUs to request that the
CPU send redundancy role switch commands to all Ethernet interfaces in that PLC that are configured for
redundant IP operation. For details on using the Service Request function, refer to the PACSystems CPU
Reference Manual, GFK-2222.
This function has an input parameter block with a length of one word.
SVC_REQ 55 is recognized in non-HSB CPUs only. This service request sends a role switch command to all
Ethernet interfaces in the PLC that are configured for redundant IP operation. The application must monitor the
LAN Interface Status (LIS) word for each Ethernet interface to determine whether the Redundant IP address is
active at that interface.
SVC_REQ 55 has no effect on Ethernet interfaces that are not configured for redundant IP operation.

SRTP Server Operation in a Redundancy System

Only the active unit maintains SRTP Server connections at the Redundant IP address and is able to respond to
SRTP requests. The backup unit does not respond to the Redundant IP address. When an Ethernet interface
changes from active to backup state, it takes down all SRTP Server connections and their underlying TCP
connections that use the Redundant IP address.
Both the active and backup units maintain SRTP Server connections at the direct IP address for network
communication with the programmer. Other remote hosts should use the Redundant IP address when
GFK-2224Q
address 0=Backup redundancy role
1=Active redundancy role
January 2017
Chapter 1. Introduction
13