Mitsubishi Electric MELSEC-Q series User Manual page 71

(10)To check logging data without stopping logging
Logging data can be checked during the logging. When checking the logging data on a display device, the data
can be checked easily by monitoring the buffer memory without stopping logging on the display device.
To check the logging data, adjust the logging cycle to prevent the logging data from being updated during read.
(a) Checking method
Read the logging data monitoring the storage places of the latest data and the oldest data in the following
buffer memory areas.
Buffer memory
CH Head pointer (Un\G1090 to
Un\G1097)
CH Latest pointer (Un\G1098 to
Un\G1105)
CH Number of logging data (Un\G1106 to
Un\G1113)
(b) Precautions
• Set CH Logging cycle setting value (Un\G1032 to Un\G1039) so that the data can be checked and read
before the logging data are updated. If the logging cycle is short, logging data may be updated while the
data are checked or read.
• After the necessary data are logged, monitor the change of the head pointer and the number of logging
data, and obtain logging data after the stored value changes.
• If the update of the data and the data being checked do not synchronize due to the logging cycle and the
scan time of the CPU module, adjust the logging cycle.
• To check data regardless of the logging cycle, use the logging hold.
Description
Check where the oldest data is stored counting from the head
address in the logging data storage area.
Check where the latest data is stored counting from the head
address in the logging data storage area.
Check the number of data stored in the logging data storage
area.
CHAPTER 4 FUNCTIONS
Reference
Page 131,
Section 6.2
(43)
Page 132,
Section 6.2
(44)
Page 132,
Section 6.2
(45)
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