Specifying an incoming message item – Echelon LNS DDE Server User Manual

Page 94

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Specifying an Incoming Message Item

Application and foreign frame messages are typically used for proprietary, non-

interoperable interfaces to L

ON

W

ORKS

devices. To receive application or foreign from

messages from a device, use the MT topic and specify the item as follows:

[device_name.]msg_in[.msg_code] [parameters]

Each component of the item format has the following meaning:

device_name

Optional. Specifies the name of an application device, as

defined in the LNS database. If not specified, the item
denotes all incoming messages addressed to the LNS DDE

Server host.

msg_in

Required. msg_in is a keyword, not a user-defined name.

This keyword is case insensitive.

msg_code

Optional. Specifies monitoring of messages with the given
msg_code, in decimal. Application message codes are from 0

to 62. Foreign frame message codes are from 64 to 78. Do

not specify message codes outside of this range. If a message
code is specified, then the data returned by the LNS DDE

Server does not contain the code. If a message code is not

specified, then the first byte of the data returned by the LNS
DDE Server contains the received message code.

Parameters

Optional.

The parameter options are:


-n bool

Specifies whether the client will receive message items from

the LNS DDE Server even if the data has not changed from
the last time this message was received from the network.
Valid values are True and False. If False, data is reported
to the client only if it has changed. If True, a byte

containing an incrementing counter will be appended to each

incoming message. If not specified, the default value
specified in the Messaging Options configuration dialog is

used.
This option may not work as expected for a series of
messages when some messages use ―nTrue and some use
―nFalse. It is recommended that you standardize on either

using this option or not then set it globally using the
Include Sequence Number option in the Network

Configuration Settings dialog.

7-2

Receiving and Sending Application Messages

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