Mitsubishi Electric MELSEC iQ-R Series User Manual page 403

Effect on the scan time
The following describes the effect on the scan time depending on the tracking mode.
For the calculation method for an increase in the scan time due to tracking transfer, refer to the following.
Page 724 Increase in the scan time due to tracking transfer
■Synchronous tracking mode
In the synchronous tracking mode, tracking transfer is always performed once every scan during the END processing. Until
the standby system receives the tracking data sent from the control system, the next scan is not started. Thus, the scan time
of the control system and standby system increases by the time for tracking data send/receive processing.
Ex.
CTRL: Program executed in the control system, MAIN: Program executed in both systems (in a redundant system without
*2
extension base units )
I/O I/O
*1 refresh refresh
Control system Control system
CPU module CPU module
Standby system Standby system
CPU module CPU module
(6)
*1 If the constant scan is used, waiting time for the constant scan is generated.
*2 In a redundant system with redundant extension base unit, the processing order in the scan is different ( Page 81 In redundant
mode), but the operation is the same as in a configuration with main base units only.
In the control system, the scan time is extended by the following tracking send processing time.
Item
(1) Tracking send (2) Waiting for completion of tracking
processing data reflection
(3) Sending tracking data
(4) Waiting for completion of tracking
data reception
In the standby system, the scan time increases by the following tracking receive processing time.
Item
(5) Tracking receive (6) Waiting for tracking data reception
processing
(7) Reflecting tracking data
Scan time of the control system CPU module Scan time of the control system CPU module
(2)
MAIN, CTRL MAIN, CTRL
Tracking data Tracking data
Data Data
reflected reflected
I/O I/O
(7)
refresh refresh
(input only) (input only)
END END
Description
After receiving a notification of the reflection completion from the standby system, the
control system sends the tracking data.
The control system sends the tracking data.
The control system waits for a notification of receive completion from the standby
system. After receiving the notification of the receive completion from the standby
system, the control system starts another END processing.
Description
The standby system receives the tracking data from the control system. After receiving
the tracking data, the standby system notifies the control system of the receive
completion and reflects the tracking data.
The standby system reflects the tracking data. After the reflection completion, the
standby system notifies the control system of the reflection completion and starts
another END processing.
END END
(1)
(3)
MAIN MAIN
(6)
Scan time of the standby system CPU module Scan time of the standby system CPU module
I/O I/O
(4)
*1 refresh refresh
Data Data Data Data
received received reflected reflected
(7)
(5)
END END
26 REDUNDANT FUNCTION
26.3 Tracking Transfer
26
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