Outline Of Explicit Message - Omron CompoNet MX2 Series User Manual

5 Message Communications
5-1

Outline of Explicit Message

Explicit Message is a Message communications function defined in the CompoNet specifications. It
uses the Node Address, Service Code, Class, Instance, Attribute, and other data to achieve Message
communications. Because the communications frame of an Explicit Message is standardized in the
CompoNet specifications, the CompoNet Communications Unit can perform Message communications
even with third-party Masters.
Explicit Messages are sent/received as follows:
In Explicit Message communication, data is sent/received basically in units of 1 byte (8 bits).
Header Node Address
Item
Header
Node Address
Service Codes
Class
Instance
Attribute
Data
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Explicit Message Communications Frame
Service Codes Class
The start of the Explicit Message. It shows that this frame is for an Explicit Message request
or a response to an Explicit Message.
This segment is set by CompoNet transparently to the user.
Request: Set the node address of the Slave/Master to send a request.
Response: The node address of the Slave/Master that returns a response is set.
Request: Set the service code for a request (read/write etc.).
Response: The service code of the requested service is returned, with the value of the most
significant bit (MSB) changed to 1.
Functional category (Major category)
Item category (Minor item)
Attribute (The set value of each function is
allocated.)
Request: Set the data to write, etc.
Response: The requested data to be read or error message is attached.
The end of the Explicit Message. It is used for the CRC check etc.
This segment is set by CompoNet transparently to the user.
Instance Attribute
Description
These show categories of each function
which are defined in the CompoNet specifi-
cations. Use these three codes to specify a
function.
CompoNet Communications Unit User's Manual (I582-E1)
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