81
Appendix C
Explicit Messages
Explicit messages sent from the Master Unit to a GRT1 Series PROFIBUS Communication Unit can be used to
read or write any parameter of a specified GRT1 Series PROFIBUS Communication Unit.
The PROFIBUS Communication Units process the commands sent from the Master and then return
responses.
C-1
Basic Format of Explicit Messages
The basic format of each command and response is shown below.
Command Block
Destination Station Address
The station address of the Unit that is sending the explicit messages (commands) is specified as a single-byte
hexadecimal.
Service Code, Class ID, Instance ID, Attribute ID
The parameters used for specifying the command, processing object, and processing content.
Note
The number of bytes designated for Class ID, Instance ID, and Attribute ID depend on the Master Unit.
When sent from an OMRON Master, the Class ID and Instance ID are 2 bytes (4 digits), and Attribute ID
is 1 byte (2 digits).
Data
Data is not required when the read command is used.
Response Block
Normal Response Block
Error Response Block
Number of Bytes Received
The number of bytes received from the source station address is returned in hexadecimal. When an error
response is returned for an explicit message, the number of bytes is always 0004 Hex.
Source Station Address
The station address of the station from which the command was sent is returned in hexadecimal.
Destination
station
address
Service
code
Class
ID
Instance
ID
Attribute
ID
Data
Number of bytes
received
Source station
address
Service code
Data
Number of bytes
received:
0004 Hex (fixed)
Source station
address
Service code
Error code
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