This manual uses many technical terms and acronyms. Some of the most commonly used are:
-
application program:
The software program you write to provide monitoring and control for your application.
-
copro:
The coprocessor that governs the exchange of data between the Hot Standby PLCs through the Sync-link between the CPUs.
-
in-rack I/O:
This term refers to local I/O directly connected to the Quantum main rack. Control of local I/O is not switched over in a hot standby application. It is only under the control of its local PLC. The logic for local I/O is written in the first section of the MAST task of the Hot Standby application program.
-
local PLC/peer PLC:
The Local PLC is the PLC in the Hot Standby system that you are working on. The other PLC is the Peer PLC. The local PLC can be the Primary or Standby and the Peer PLC can be the Standby or Primary.
-
main rack:
This is the rack that supports the processors (CPU module and RIO Drop adapter modules (140 CRA 93• 00, 140CRA31200 or BMX CRA 312 •0). Local I/O may be placed in the main racks, but it is not part of the Hot Standby system because it is controlled only by a local PLC, not by a peer PLC.
-
program cycle:
In a Hot Standby system, the program cycle can only use the MAST task, see
Exclusive Use of MAST Task. The MAST task cycle is divided in the four main parts:
-
input drivers: all input modules associated with the MAST Task are scanned
-
Hot Standby system functions: data exchange between CPU and Copro and system checks
-
user logic execution: the system executes the application program relative to the MAST Task
-
output drivers: the system applies the outputs evaluated during the application program execution to all the output modules associated with the MAST Task
-
switchover:
The moment when application control transfers from the Primary controller to the Standby controller. The switchover event has a finite duration. It can be initiated:
