Eaton easyE4 User Manual

6. Function blocks
6.1 Manufacturer function blocks
6.1.7.10 MU - Acyclical Modbus RTU request
Only available on easySoft Version 7.40 or higher.
Only available on firmware version 1.40 or higher.
Otherwise this option will not be available.
General
easyE4 base devices provide 32 acyclical Modbus RTU request
function blocks, MU01 through MU32.
An MU function block sends exactly one acyclical request to the
selected Modbus RTU slave. This function block is available for
all programming languages and all easyE4 base devices.
MU function blocks cannot be used within a user
function block.
They are primarily used in order to request acyclical values such
as temperatures or to request fixed values once when the pro-
gram is starting.
Operating principle
An acyclical Modbus RTU request function block will send exactly one acyclical
request to the selected Modbus RTU slave as soon as there is a rising edge at trigger
coil T_ and function block EN=1. Function code FC3 will be set as the acyclical
request by default. The data associated with the request will be read in the easyE4
base device in a defined marker range or written from there. After the data is trans-
ferred successfully, the slave will respond and the RY function block output will
switch to a state of 1.
The QV function block output indicates the number of elements transferred.
The following function applies to FC23:
l
The QV function block output indicates the number of elements read.
l
The QV function block output indicates the number of elements written. QN
remains equal to 0 for other function codes.
Like with cyclical data communication, a response time can be defined here as well.
As soon as the slave does not respond within the specified time, function block out-
put E1 will be set to a state of 1. Whether the registers are cleared when there is a
timeout will depend on the setting configured with the option of the same name
under Project view / Cyclical data tab when the Modbus RTU slave module is selec-
ted previously – please refer to → "Cyclical data tab", page 782 as well.
If an MU function block is used in the program without Modbus modules having been
configured first, the plausibility check will report errors.
538
easyE402/24 MN050009ENEaton.com

Eaton easyE4 Specifications

General

Brand	Eaton
Model	easyE4
Category	Relays
Language	English