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

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Publication 1769-UM001B-EN-P - October 2002
B-22 Explicit Messaging Application Examples
Get 1769 I/O Module Configuration Size
1769 I/O modules should be configured in RSNetworx for DeviceNet
when your DeviceNet system is configured. We’ll describe how to
modify 1769 I/O module configuration parameters while the system is
running. Modifying I/O module configuration parameters dynamically
is not a common practice, but for some applications it may be
necessary. Refer to the Ladder Logic Example Program on page B-30
for the necessary logic for this command.
We’ll use a 1769-OF2 analog output module to get/set configuration
parameters dynamically for this example.
The first task is to determine the size of the configuration file for the
1769 I/O module. The following command will read the number of
configuration words (not bytes) from the 1769-OF2 in slot 10 of the
remote DeviceNet system by sending the following command:
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
0017 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. “030C” hexadecimal 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 configuration file size.
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.
“0017” hexadecimal (23 decimal) means Module Configuration Size. The attribute data size is one word.