Rockwell Automation 1769-ADN Compact I/O 1769-ADN DeviceNet Adapter User Manual
Page 174
Publication 1769-UM001B-EN-P - October 2002
B-16 Explicit Messaging Application Examples
Following each command reply, the user program must MOVe a
command value of 4 hexadecimal to the appropriate M0 file word to
clear the previous reply from its buffer, making it ready for the next
command.
The following illustrates the Get 1769-ADN 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
0001
Class
7
0001
Instance
8
0005
Attribute
9
Reply (Hexadecimal)
Description (High Byte/Low Byte)
0101
TXID
1
/Status
0002
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. “1” hexadecimal is the class code for the identity object. The class
data size is one word.
8
Instance identifies the specific instance within the object class towards which the transaction is
directed. “0001” hexadecimal is the instance of the identity object in the 1769-ADN. The instance data
size is one word.
9
Attribute identifies the specific characteristic of the object towards which the transaction is directed.
“0005” means Status. The attribute data size is one word.