4 FUNCTIONS
4.13 Logging Function
63
4
■
Head pointer and latest pointer
The storage location of the oldest data and the latest data in CH1 Logging data (Un\G10000 to Un\G19999) can be checked
with the following buffer memory areas.
• When the number of collected data points is less than 10000
• When the number of collected data points is 10001 or greater
The head pointer does not change until CH1 Logging data (Un\G10000 to Un\G19999) becomes full after the logging start
(fixed to 0).
When CH1 Logging data (Un\G10000 to Un\G19999) becomes full and overwriting the data starts from the start address, the
head pointer increases by one each time new data is stored.
■
Checking logging data without stopping the logging operation
Logging data can be checked during the logging operation with 'CH1 Head pointer' (Un\G434), 'CH1 Latest pointer'
(Un\G435), and 'CH1 Number of logging data' (Un\G436).
To check logging data during logging operation, follow the precautions below because logging data may be refreshed while
data is being read out.
• Set the cycle to 'CH1 Logging cycle setting value' (Un\G537) so that data checking and reading surely complete before
logging data is refreshed. If the logging cycle is short, logging data may be refreshed during data checking and reading.
• After obtaining the logging data which needs to be checked, monitor the variation of the head pointer and the number of
logging data, and obtain logging data just after the stored value has changed.
• If the data refreshed and the data being checked do not synchronize due to the relationship between the logging cycle and
the scan time of the CPU module, adjust the logging cycle.
Stop the logging operation when the logging data needs to be checked without paying attention to the logging cycle.
(
Page 64 Stopping the Logging Operation)
Buffer Memory Areas
Description
CH1 Head pointer (Un\G434)
The buffer memory address of the oldest data in CH1 Logging data (Un\G10000 to Un\G19999) can be
checked with this buffer memory area. The offset value (0 to 9999) counted from the start address of
CH1 Logging data (Un\G10000 to Un\G19999) is stored.
CH1 Latest pointer (Un\G435)
The buffer memory address of the latest data in CH1 Logging data (Un\G10000 to Un\G19999) can be
checked with this buffer memory area. The offset value (0 to 9999) counted from the start address of
CH1 Logging data (Un\G10000 to Un\G19999) is stored.
the latest
the oldest
Address 0
Address 1
Address 2
Address 3
Address 4
Address 5
Address 9998
Address 9999
CH1 Head pointer
= 0
CH1 Latest pointer
= 5
the latest
the oldest
Address 0
Address 1
Address 2
Address 3
Address 4
Address 5
Address 9998
Address 9999
CH1 Head pointer
= 5
CH1 Latest pointer
= 4
Summary of Contents for MELSEC iQ-F
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Page 9: ...7 MEMO ...
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