C2000H Duplex System - Omron C1000H Installation Manual

C2000H Duplex System

3-2

C2000H Duplex System

Operating Mode
Peripheral Devices
Initial Settings
1, 2, 3...
The C2000H has a unique feature. The C2000H lets you build a PC that uses
two CPUs. This is called a Duplex System. Either CPU, which is mounted to the
CPU Rack, is capable of assuming the system function. One CPU controls the
system while the other CPU assumes a standby status. Consequently, if a failure
occurs in one of the CPUs, the other CPU can take over the system function,
preventing the entire system from halting, The figure below shows a Duplex Sys-
tem. Note that the CPU Rack is connected to the I/O Rack by two cables.
CPUs
While the Duplex System is in operation, one of the two CPUs has "active" status
and the other CPU has "standby" status. The active CPU executes the program
and controls the I/O Units while the standby CPU merely executes the program,
but does not control the I/O Units. The status of the CPUs can be determined by
setting the selector switch on the front panel of the Duplex Unit.
If an error occurs in the active CPU, making further operation impossible, the
standby CPU automatically becomes active and takes over operation. The
failed CPU can be repaired or replaced without having to shut down the entire
CPU.
The operating mode is set through the active CPU. Once the operating mode of
the active CPU is set, the standby CPU is automatically set in same operating
mode as the active CPU.
As mentioned, the operating mode can only be set through the active CPU. How-
ever, peripheral devices such as the Programming Console can be mounted to
the standby CPU to monitor operations.
Take the following steps to prepare the Duplex System for operation.
1. Be sure to install identical Memory Packs in both CPUs. Because one of the
CPUs in the Duplex System acts as a standby system, make sure that identi-
cal Memory Packs are installed in both CPUs. IF the active CPU can no
longer control the system, the standby CPU can take over the System using
an identical program.
ROM Packs When using ROM Packs, make sure that the same number and
same type of EPROM chips are mounted to both ROM Packs. In addition,
the same program must be written to both ROM Packs.
RAM Packs When using RAM Packs, make sure the Units have the same
memory capacity. Write the program to the RAM Unit installed in the active
CPU. The program written to the active CPU is automatically written to the
memory of the standby CPU when the Duplex System is put into operation.
CPU Rack
Duplex Unit
I/O Rack
Section 3-2
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