Buffer Capacity - Mitsubishi MELSEC Q series User Manual

6.6

Buffer Capacity

Buffer capacity means the size of the buffer that is used to temporarily store collected data.
CPU module
Device
area
Sampled data are stored in the specified buffer. The data in the buffer are saved to the SD memory card at the timing
of file saving.
Data logging buffer capacity
(1) Buffer capacity setting
Increasing the buffer capacity enables the following.
• Continuous logging: Processing overflow occurs less frequently.
• Trigger logging: The number of sampled data is increased.
• Specification period logging: Processing overflow occurs less frequently.
*1 Adjust the buffer capacity while checking the special register (Free buffer space). When the free buffer space is
insufficient even though the buffer capacity is increased, perform the following actions.
• Increase the sampling interval. ( Page 115, Section 8.4.4)
• Decrease the number of sampled data. ( Page 117, Section 8.4.5)
• Decrease frequency of file switching. ( Page 127, Section 8.4.12)
• Cancel the "File Transfer" setting in the data logging setting. ( Page 129, Section 8.4.13)
To consider the processing time taken to data logging, refer to  Page 161, CHAPTER 10.
(2) Buffer utilization
The buffer utilization can be obtained by a formula, "number of device points  2 bytes + 2 bytes". Note that, if
output of the following column is selected, the corresponding amount is increased.
• Date column: 10 bytes
• Data sampling interval column: 8 bytes
• Execution step No. column: 10 bytes
• Execution program name column: 8 bytes
• Index column: 4 bytes
Ex. Outputting data in all columns as data to be sampled by data logging when 128 points is assigned to one
setting (Maximum setting)
128  2 + 2 + (10 + 8 + 10 + 8 + 4) = 298 bytes
68
Buffer
Specified
<Setting 1>
device data
sampling
1st sampling data
2nd sampling data
<Setting 2>
1st sampling data
2nd sampling data
Item
Buffer capacity for setting 1
Buffer capacity for setting 2
For each setting, any of 32 to 4832K bytes (in increments of 1K byte) can be specified.
The total capacity for the settings No.1 to No.10 is 5120K bytes (maximum).
* 1
SD memory card
<Setting 1>
1st sampling data
2nd sampling data
<Setting 2>
1st sampling data
2nd sampling data
Setting range
* 1