Mitsubishi Electric MELSEC iQ-R User Manual page 103

■Precautions for creating the program
• The function block for continuous logging data transfer reads out the data to the file registers each time 5000 point data
sets are stored in the A/D converter module. The approximate processing time of the function block is obtained by adding
up the required time of following instruction operations used in the function block: five times of the FROM instruction (1000
*1
points) , nine times of the FROM instruction (1 point)
of all instructions used in the function block. For details on the processing time of each instruction used in the function
block, refer to MELSEC iQ-R Programming Manual (Instructions, Standard Functions/Function Blocks).
• To prevent logging data omission, create the program where the function block is executed once or more times in 20ms
(The processing time of this program must be 20ms
• The following table (at the bottom row) shows the formula to calculate the approximate number of channels available for
data transfer to the file registers with the function block. Note that this applies to the case when a user do not create any
program.
Item
Processing time (as a guide) of the function
block for continuous logging data transfer
Number of channels (as a guide) available
for data read
*1 Maximum processing time of each instruction is used for the calculation. ( MELSEC iQ-R Programming Manual (Instructions,
Standard Functions/Function Blocks))
*2 This value is for when the continuous logging is executed every 5s cycle. When using the continuous logging cycle different from 5s,
apply the value obtained from T(ms) below for the calculation of the number of channels.
T(ms) = (Continuous logging cycle (s)  5000 (points))  1000 - 5 (ms)
The calculation result of 63 channels, which is the number of channels available for data read, is a value for the case when
the program consists of only the function block for continuous logging data transfer. If the other processing is added to the
program, or another program is added, the number of channels available for the continuous logging decreases. Please
consider an actual application and configure the system.
*1
. If the exact processing time is required, add up the processing time
*2
or shorter including the processing time of the function block.)
Calculation formula
= (Processing time of the FROM instruction (1000 points))  (5 times) + (Processing time of the FROM instruction
(1 point))  (9 times)
*1 *1
 5 + 4.3s  9
= 55.6s
= 316.7s
*2
 (Processing time (as a guide) of the function block for continuous logging data transfer)
= 20ms
= 20ms  316.7s
= Approx. 63 channels
1 FUNCTIONS
1.15 Continuous Logging Function
1
*2
.
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