Mitsubishi MELSEC Q Series User Manual

4
FUNCTIONS
4.4 MELSECNET/H Module Access Function
4.4.4 Link device refresh setting
4 - 26
1
OVERVIEW
2
SYSTEM CONFIGURATION
3
SPECIFICATIONS
4
FUNCTIONS
5
SETTING AND PROCEDURES
6
I/O NUMBER ASSIGNMENT
7
MEMORIES AND FILES
8
INSTALLING / UNINSTALLING
4.4.4 Link device refresh setting
Link device refresh setting is required to use the internal buffer access in the user
program.
To enable the link device refresh, set the link device refresh cycle and refresh parameters
on the MELSECNET/H utility.
(1) Link device refresh cycle
The link device refresh cycle is a cycle for mutually refreshing the internal link device
buffers of the C Controller module and the link devices of the MELSECNET/H module.
The concept of the link device refresh cycle is shown below.
(a) Total link devices refresh time
1) Total link devices refresh time
The total link devices refresh time is a processing time for refreshing the link
devices of all the MELSECNET/H modules controlled by the C Controller
module.
2) How to obtain total link devices refresh time
The theoretical value of the total link devices refresh time can be obtained by a
calculation formula. ( Section 4.4.5 (2))
3) Variation in total link devices refresh time
The total link devices refresh time varies depending on the operating
conditions of the C Controller system.
The time may increase when interrupt processing or high-priority task
processing (e.g. Tornado's Shell command or bus interface driver processing)
is performed during link device refresh.
Figure 4.19 Conceptual illustration of link device refresh cycle
Figure 4.20 Variation in total link devices refresh time
C Controller
module processing
Link device
refresh
Link device
refresh
Link device
refresh
Link device
refresh
Link scan
Start End
Link device
refresh
Link device
refresh cycle
Link device
refresh cycle
Link device
refresh cycle
Total link devices refresh time
Interrupt
processing
Total link devices
refresh time
increases.
High-priority task
processing
Link devices refresh processing
C Controller
module processing
Link device
refresh
Link scan
Link device
refresh cycle

Mitsubishi MELSEC Q Series Specifications

General

Brand	Mitsubishi
Model	MELSEC Q Series
Category	Controller
Language	English