7BChapter Four: Operation 69BDeviceNet Messaging Protocol
47
CAN Identifier Field
The CAN Identifier Field is a single 11-bit field that defines the components of a DeviceNet
connection (Table 17, page 48). This information is required for both explicit and I/O poll
messaging connections. The CAN Identifier Field consists of the following three components:
• Message ID (Group 1 or 2)
• Node Address (network address)
• Message Ty
pe ID
Message ID
This fixed 2-bit field indicates the ty
pe of messaging used in the device.
The identifier for Group 2 m
essages is fixed with bits 10 and 9 set to 1 and 0 respectively.
The identifier for Group 1 messages is fixed with bits 10 and 9 set to 0 and 1 respectively.
Node Address
The Node Address is a 6-bit field that identifies the network address of the device as a
hexadecimal value. The source node address is the address of the device sending the m
essage.
The destination node address is the address of the device receiving the message.
In a request m
essage, the device address in the CAN Identifier Field is the destination node
address. In a response message it is the source node address.
Message Type ID
This 3-bit field identifies the specific ty
pe of message (explicit or I/O) and whether the m
essage
string is a request or a response. The message type IDs are fixed for the Predefined Master/Slave
Connection Set [1].
Note
The CAN Identifier Field is represented by a single hexadecimal value in each
message string.
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