Refresh Cycle - Mitsubishi Electric MELSEC iQ-R Series User Manual

Refresh cycle

The following shows how to calculate the refresh cycle.
For the setting method of refresh cycle, refer to the following:
Page 181 FIXED CYCLE PROCESSING FUNCTION
How to decide the refresh cycle
Follow the procedure below to decide the refresh cycle.
1.
Calculation of the total link refresh time
2.
Preliminary decision of the refresh cycle
3.
Pre-operation of a system of this product
4.
Decision of the refresh cycle
■Calculation of the total link refresh time
The total link refresh time is equal to the sum of the link refresh time of all of the network modules controlled by this product.
The total link refresh time of the system of this product in operation can be checked with the special registers (SD526 to
SD531).
For the calculation method of link refresh time for each network module, refer to the following:
Page 172 Link refresh time
■Preliminary decision of the refresh cycle
Set the value which satisfies the following relational expression to the refresh cycle and total link refresh time.
• Refresh cycle > Total link refresh time
■Pre-operation of a system
Confirm whether the system of this product operates correctly by the refresh cycle which is decided preliminarily.
If the processing of this product cannot be completed within the refresh cycle, a 'refresh cycle exceeded (1846H)' error
occurs.
Take the corrective actions shown below in order for the system to operate correctly when the system of this product operates
abnormally.
Corrective action
Increase the refresh cycle setting
value.
Reduce the number of set refresh
points.
16 NETWORK MODULE ACCESS FUNCTION
174
16.3 Processing Time
Description
Set the refresh cycle again by using the link refresh time (the maximum value) as a reference so that the following
relational expression is satisfied.
• Measured value of link refresh time (maximum value) < Refresh cycle
Review the number of refresh points in refresh parameter settings.