7
- 2
7.1 Instructions Restricted in Use for Redundant System
7
PROGRAMMING CAUTIONS
(b) Countermeasures
1) The instruction that includes the complete signal can be executed again by the
new control system CPU module, if it has been suspended due to system
switching.
*2
However, note that the same instruction might be executed twice.
[Example]
In the following program example, when system switching occurs during
execution of the REMFR instruction (M201 : ON) in an MELSECNET/H remote
I/O system, the REMFR instruction is re-executed by the new control system
CPU module.
• System configuration
Diagram 7.1 shows the system configuration for the example of the
REMFR instruction programming.
• Relevant devices
Table7.2 indicates the devices used in the program example for the
REMFR instruction.
* 2: The complete signal is not tracked even it is set for tracking.
Diagram 7.1 System Configuration
Table7.2 Devices Used for Execution of REMFR Instruction
Device No.
Name
Remarks
SB20
Module status
Refer to the following manual for details of
the link special relays (SB) and link special
registers (SW).
Q Corresponding MELSECNET/H
Network System Reference Manual
(Remote I/O Network)
SB47
Baton pass status of host
SB48
Status of host
SB49
Data link status of host
SW70.9
Baton pass status of each station (10th station)
SW74.9
Data link status of each station (10th station)
SM1518
Standby system to control system switching
status flag
----
M200
Read request flag
Change the device number according to the
system.
M201
REMFR instruction execution flag
M202
System switching-triggered REMFR instruction
re-request flag
M203
REMFR instruction completed flag
M204
REMFR instruction abnormally completed flag
Control system
Standby system
Station No. 10
Station No. 2
Tracking cable
Target intelligent function module of
REMFR instruction (I/O No.: 10H)
MELSECNET/H remote I/O network Network No. 1