Mitsubishi Electric MELSEC iQ-R Series User Manual page 40

Trigger buffer utilization
When the trigger logging is specified, the internal memory (trigger buffer) of the high speed data logger module is used to
temporarily store the data before and after the trigger occurrence.
The setting which exceeds the total trigger buffer utilization (20 MB (20971520 bytes)) on the high speed data logger module
cannot be configured.
The trigger buffer utilization can be obtained by the following formula.
Trigger buffer utilization per single data logging = ((device points  2 + 88)  (total number of lines +1))  2
■Number of device points
The device points of data types per one data logging are as follows:
Data type
Bit
Word [Signed]
Double Word [Signed]
Word [Unsigned]/Bit String [16-bit]
Double Word [Unsigned]/Bit String [32-bit]
FLOAT [Single Precision]
FLOAT [Double Precision]
16bit BCD
32bit BCD
String
Raw
*1 If the size is in odd number, the device point will be rounded up by adding 1 point.
*2 For double word device, the device becomes 2 points for each 4 bytes. The fraction should be rounded up to 2 points.
(Assign 2 points if size is 4 and 4 points if size is 5)
■Total number of lines
The total number of lines indicates the value set in the [Number of Logging Lines] tab on the "Data logging setting" screen.
(Page 160 Number of logging lines)
However, calculate as 100 lines if the total number of lines is less than 100 lines for high speed sampling. Calculate as 30
lines if the total number of lines is less than 30 lines for general sampling.
Ex.
When performing trigger logging in high speed sampling with all the 64 words [Signed] and on total 100 lines
Trigger buffer utilization per single data logging = (((64  1)  2 + 88)  (100 + 1))  2 = 43632
Trigger buffer usage rate = 43632 / 20971520  0.2%
1 FUNCTION
38
1.1 Data Logging Function
Number of device points
1 point
1 point
2 points
1 point
2 points
2 points
4 points
1 point
2 points
*1*2
(Specified size  2) points
*1*2
(Specified size  2) points