Allen-Bradley Compact I/O 1769-ADN DeviceNet, User Manual

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Publication 1769-UM001B-EN-P - October 2002
Explicit Messaging Application Examples B-19
The following illustrates the Get 1769 Module Status command and
the command reply:
Command (Hexadecimal) Description (High Byte/Low Byte)
0101 TXID 1 /Command 2
0006 Port #
3
/Byte Count
4
0E13 Service 5 /Mac ID 6
030C Class
7
00xx Instance 8
000C Attribute
9
Reply (Hexadecimal) Description (High Byte/Low Byte)
0101 TXID
1
/Status
0001 Port # 3 /Byte Count 4
8E13 Service
5
/Mac ID
6
xxxx Status Word from Adapter
1 TXID (Transmission ID) is used by the scanner to track the transaction to completion and returns the same
value with the reply. To properly track commands with their replies, this value should be incremented for
each new command sent. TXID size is one byte.
2 Command instructs the scanner on how to administer the request. “01” is the Execute This Transaction
Block command. The command data size is one byte. Refer to the 1747-SDN User Manual , publication
1747-5.8, for list of supported commands.
3 Port # is the physical channel of the scanner where the transaction is to be routed. The port # must be 0
(channel A) and the data size is one byte.
4 Byte Count identifies the number of bytes in the transaction body. The transaction body begins with
word 3 and the data size is one byte.
5 Service specifies the type of request being delivered. “0E” is a Single Parameter Read. In the reply, the
high bit of this byte is set, so 8E represents the reply to the 0E service. Service data size is one byte.
6 Mac ID is the DeviceNet network node address of the device for which the transaction is intended. The
slave device must be listed in the scanner module’s scan list and be online for the explicit message
transaction to complete successfully. The Mac ID value must be hexadecimal. In this example, the node
address of the 1769-ADN adapter is 19 decimal or 13 hexadecimal. The Mac ID data size is one byte.
7 Class is the desired DeviceNet class. “030C” is the class code for the object representing 1769 I/O.
The class data size is one word.
8 Instance represents the slot number of the I/O module from which we want the status information. This
analog output module is in slot 10 or “000A” hexadecimal.
9 Attribute identifies the specific characteristic of the object towards which the transaction is directed.
“000C” means Module Status. The attribute data size is one word.
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