69BDeviceNet Messaging Protocol 7BChapter Four: Operation
48
Table 17: CAN Identifier Field
10 9 8 7 6 5 4 3 2 1 0
Group 2
Message ID
Fixed 2-bit value
Node Address
Hexadecimal Value—6-bits
Group 2 Message
Type ID
Fixed 3-bit value
1 0 Destination Node Address 1 0 0
Master’s Explicit Request
1 0 Source Node Address 0 1 1
Slave’s Explicit Response
1 0 Destination Node Address 1 0 1
Master’s I/O Poll
Command
1 0 Destination Node Address 1 1 0
Group 2 Only
Unconnected Explicit
Request Messages
1 0 Destination Node Address 1 1 1
Duplicate Node Address
Check Messages
Group 1 Message
ID
Fixed 2-bit value
Group 1 Message
Type ID
Fixed 3-bit value
Node Address
Hexadecimal Value—6-bits
0 1 1 1 1 Source Node Address
Slave’s I/O Poll Response
CAN Data Field
The CAN Data Field is a series of 8-bit fields that defines the specific parameters of an explicit
message. This information is not required in I/O poll messages per the Predefined Master/Slave
Connection Set [1].
The CAN Data Field is required in every explicit message; however, the format of the field varies
depending on whether the message is a request or a response.
The CAN Data Field consists of a message header and a message body (Table 18, page 49). The
m
essage header is a single 8-bit field, consisting of three com
ponents that define the basic
communication information about the explicit message. The header includes the same
information regardless of whether the message is a request or a response.
The explicit message header consists of the following three components:
• Fragment Bit
• Transaction ID (XID) Bit
• Node Address
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