Data Communications In A Redundant System - Mitsubishi Electric QJ71E71-100 User Manual

14.7.4

Data communications in a redundant system

This section describes data communications using the E71 mounted on the main base unit in a redundant system.
Processes other than those described in this section are the same as those in a single CPU system.
(1) Initial process
(a) Reinitialization process
When performing a reinitialization process, do not change the settings, such as the own station IP address and
Ethernet operation setting. Doing so may cause a communication error.
• When using the UINI instruction
Execute the instruction after specifying "0
• When directly writing to the buffer memory
Write "1" to the bit 15 of Communication condition setting (Ethernet Operation Setting) area (address: 1F
without changing the value stored in the buffer memory area.
(b) Initial process using I/O signals
Because the output signal (Y) turns off in the standby system CPU module, an initial process cannot be
performed using I/O signals. To perform an initial process, set the network parameters using a programming
tool.
(2) Open/close processes
(a) Communications in TCP/IP
Place the E71 in open wait status (Passive open) and perform an open/close process from the connected
device. If an Active open process is performed from the E71, the close process is performed from the E71 after
data communications, but if the system is switched before execution of the close process, the process cannot
be performed.
(b) When using a user connection to communicate with the standby system (for MC
protocol communications or communications using a random access buffer)
• Ethernet operation setting
Set "Always wait for OPEN (Communication possible at STOP time)" under "Initial timing".
• Open setting
In TCP/IP communications, set "Unpassive or Fullpassive" under "Open system".
Setting connections for communications with the system A and communications with the system B is recommended. This
facilitates communications with the other system if a communication error has occurred in the own system or when the
system is switched. A maximum of 16 user connections can be registered in the E71.
(c) Open/close processes using I/O signals
Because the output signal (Y) turns off in the standby system CPU module, open/close processes cannot be
performed using I/O signals. To perform the processes, set "Always wait for OPEN (Communication possible at
STOP time)" under "Initial timing" in the Ethernet operation setting or use dedicated instructions
(OPEN/CLOSE instructions).
" for Specification of changed item ((S1)+2) of the control data.
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