Buffer Capacity - Mitsubishi Electric MELSEC-L 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.
• Trigger logging: The number of sampled data is increased.
• Continuous 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. (
• Decrease the number of sampled data.
• Decrease frequency of file switching. (
(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
Outputting data in all columns as data to be sampled by data logging when 128 points is
Ex.
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 4832 k bytes (in units of 1 k byte) can be specified. The
total value of settings No.1 to No.10 is up to 5120 k bytes.
*1
Page 99, Section 8.4.4)
Page 101, Section 8.4.5
Page 109, Section 8.4.10)
SD memory card
<Setting 1>
1st sampling data
2nd sampling data
<Setting 2>
1st sampling data
2nd sampling data
Setting range