ProSoft Technology PTQ-PDPMV1 - Manual (Page 192)

Hot Standby Support PTQ-PDPMV1 ♦ Quantum Platform
User Manual PROFIBUS DP Master Network Interface Module for Quantum
Page 192 of 306 ProSoft Technology, Inc.
August 12, 2014
7.2.4 Hot Standby States
State Description
There are three normal running states of operation in a general Hot Standby
system.
 PRIMARY: The PLC is set as the Primary CPU and controls the Input/Output
process as if it is stand-alone.
 STANDBY: This PLC is set as the Standby CPU and is ready to take over as
Primary at all times, but the Primary CPU controls process and network.
Outputs are not applied.
 OFFLINE: The PLC is set to offline mode and the CPU cannot act like a
Primary or Standby CPU.
It may be in STOP or disconnected mode. Here the PLC behaves as a normal
non-HSBY CPU.
The equivalent states for the Master module are "Not connected", "Active", and
"Passive" (bold text in the illustration above).
 NOT CONNECTED: The Master module would be disconnected from the
PROFIBUS network.
 ACTIVE: The Master module would act as a class 1 PROFIBUS DPV1
Master, managing I/O data, acyclic data, alarms, diagnostic and parameter
data with its assigned slaves as if it were stand-alone.
 PASSIVE: The Master module would monitor the status of the local (active)
Master, and if it detects any problems, it would inform the application about
the situation. Note that the remote (passive) Master would not switch to local
(active) unless the application tells it to do so.