12.1 Data Logging
12.1.2 Scan Setting Guidelines
12-12
This timing chart illustrates the logging process when performed synchronously with the scan.
The logging processes for sampling the data and writing it to a file are performed within the
scan cycle. Therefore, the scan cycle (time period A in the above chart), must be set to a value
greater than the current scan time (time period B in the above chart).
If the scan cycle is shorter than the current scan time, a scan time over limit error will occur and
the count of SW00044 (H Scan Exceeded Count) or SW00046 (L Scan Exceeded Count) will
be incremented. This can also cause a Watchdog Timer Error (E.001) or cause the CPU to go
down.
Set the scan time so that it is long enough to log the number of registered data items.
If Logging Is Asynchronous with the Scan
The scan setting for logging asynchronously with the scan should be set as given below.
Note: These values are for word data without an application. Set the scan setting according to the application
usage conditions (number of registers to log, register types, ladder programs, etc.).
Storage Location
Scan Setting Guideline
Built-in RAM disk
0.250 ms min.
USB memory
0.500 ms min.
Logging
(data
s
ampling)
High-
s
peed
or
low-
s
peed
s
can
DWG.H
Logging
(data
s
ampling)
Logging (file writing)
Logging (file writing)
A:
S
can cycle
B: Current
s
can time
DWG.H or
DWG.L
Thi
s
proce
ss
s
ample
s
target data and load
s
it
into a logging buffer.
Thi
s
proce
ss
write
s
data
that wa
s
s
ampled during
the
s
can to the log file.
