Missing Data; Conditions Under Which Missing Data Occurs - Mitsubishi Electric MELSEC iQ-R Series User Manual

20.9

Missing Data

The term "missing data" means that some of the collected data is missing, resulting in data discontinuity.

Conditions under which missing data occurs

Missing data occurs under the following conditions:
Item
Processing overflow
Operations for the CPU module
Operation from engineering tools, CPU Module
Logging Configuration Tool, and external devices via
protocols such as FTP, SLMP, and MC
*1 Failure to collect data at the specified collection interval/timing due to the execution of a long-running instruction (such as FMOV) does
not cause processing overflow or missing data.
*2 The following operation also is included:
 Online operation which displays data by operation such as read from the programmable controller performed from an engineering tool
(retrieval and display of a list of files on the CPU module)
 View of the event history (retrieval of the event history from the CPU module)
Processing overflow
In normal cases when the usage of the internal buffer reaches the specified maximum capacity, the CPU module overwrites
the data stored in the storage memory on a first-in first-out basis. If the internal buffer becomes full before all of the data stored
in it is saved to the storage memory, however, the CPU module does not overwrite the existing data and stops storing data in
the internal buffer, thus resulting in missing data. This situation is referred to as processing overflow. Upon the occurrence
overflow, the special register (Number of processing overflow occurrences) stores the number of times when processing
overflow occurred.
20 DATA LOGGING FUNCTION
288
20.9 Missing Data
Description
Processing overflow has occurred due to failure to keep up with the specified collection interval/timing.
The CPU module has been stopped and run with "Operation at transition to RUN" set to "Auto Start".
The CPU module has been turned off and on with "Operation at transition to RUN" set to "Auto Start".
The CPU module has been reset and run with "Operation at transition to RUN" set to "Auto Start".
• When the CPU module is suspended and restarted, and operation for displaying the logging state is
performed from CPU Module Logging Configuration Tool
*2
• File read , write, delete, or verification
*1