Communication Using The Random Access Buffer; Communications Using A Dedicated Instruction; When The Control System Ip Address Is Used; Processing When A Dedicated Instruction Abnormally Ends - Mitsubishi Electric MELSEC iQ-RJ71EN71 User Manual

Communication using the random access buffer

Because tracking is not performed on the buffer memory of the Ethernet-equipped module, when writing data to the random
access buffer, write the same data to the control and standby systems.

Communications using a dedicated instruction

■System switching during dedicated instruction execution
When systems are switched during execution of a dedicated instruction, the dedicated instruction may not be completed.
Execute the dedicated instruction again from the control system CPU module after system switching.

■When the control system IP address is used

When using dedicated instructions for the Ethernet-equipped modules of a redundant system, the same IP address can be set
for both systems A and B by setting the control system IP address for the external device IP address in the control data. (
Page 226 Both systems identical IP address setting function)
■Specification of the target station CPU type in dedicated instructions
For a dedicated instruction in which the target station CPU type is specified as a control data, the control system CPU,
standby system CPU, system A CPU, and system B CPU can be accessed by specifying the type. By specifying the access
destination CPU module, even if system switching occurs due to a communication error, access to the specified CPU module
is possible using the communications path bypass function. ( MELSEC iQ-R Programming Manual (CPU Module
Instructions, Standard Functions/Function Blocks,  MELSEC iQ-R Programming Manual (Module Dedicated Instructions))

■Processing when a dedicated instruction abnormally ends

When the dedicated instruction is executed by specifying the access destination CPU module, it may be completed with an
error if systems are switched in the target station. If the dedicated instruction was completed with an error, execute it again.
■SEND instruction
• When the target station is in a redundant system, the communication request source station must identify that the target
station is the control system to execute the SEND instruction. When the target station is the standby system, the RECV
instruction is not executed at the target station after data is sent by the SEND instruction, and the target station storage
channel becomes occupied and unable to be used.
• When a redundant system exists in a network where broadcast communications are performed, the RECV instruction is not
executed at the standby system, and the storage channel becomes occupied and unable to be used.
■RECV and RECVS instructions
• When the SEND instruction is executed for the control system, if the systems are switched before execution of the RECV
instruction and interrupt program, the control system retains 'RECV instruction execution request' (Un\G5301) and the
interrupt program interrupt factor (interrupt pointer). If system switching occurs again, and the standby system is switched
to the control system, the RECV instruction and interrupt program will be executed by the retained 'RECV instruction
execution request' (Un\G5301) and interrupt program interrupt factor.
• When the SEND instruction is executed for the standby system, and the standby system receives data from the sending
station, the standby system retains 'RECV instruction execution request' (Un\G5301) and the interrupt program interrupt
factor (interrupt pointer). Therefore, when the standby system is switched to the control system due to system switching,
the RECV instruction and interrupt program will be executed by the retained 'RECV instruction execution request'
(Un\G5301) and interrupt program interrupt factor.
■REQ instruction
When performing remote STOP or remote RUN on a redundant system, do as follows: Perform STOP on the standby system
 STOP on the control system  RUN on the control system  RUN on the standby system.
1 FUNCTIONS
232
1.17 Redundant System Function