Jetter JVM-407B-HMI, User Manual

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JVM-407B Programming
Operating principle
The application program monitors the activity of a client communicating with a
server of the device JVM-407B by means of two special flags and one special
register per interface.
The illustration below shows the interdependence between interface activity
and the two special flags, as well as the special register:
Telegrams
OS Flag
User Flag
Timeout
Application program:
WHEN OS_FLAG Continue
User_FLAG := TRUE;
1
2
3
4
Number Element Description
1 Telegrams The client places requests to the server.
2
OS flag OS flag set by the device JVM-407B after
receiving a request
3
User flag You must set the user flag in the application
program once the device has set the OS
flag.This indicates that the connection has
temporarily been disrupted even if the device
resets the OS flag very quickly.
4
Timeout Time of inactivity after which the OS resets both
special flags. This time can be set in a special
register.
Interface activities are monitored as follows:
Step Description
1
Enter the desired value into the timeout register of the application
program. This way, the monitoring mode is activated as well.
2 When the controller receives the next telegram, the device JVM-407B sets
the corresponding OS flag.
3 If the OS flag has been set, the application program also sets the
respective user flag.
4
Each new telegram causes the timeout to restart.
5 If telegrams cease to arrive, both special flags are reset by the controller
upon expiry of the timeout interval.
Introduction
Overview
Description