Ntellisys, Daptive, Ressure – Nor-Cal Intellisys Adaptive Pressure Controllers User Manual
Page 24: Ontrollers, 2 - establishing a devicenet connection
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8.2 - Establishing a DeviceNet connection
This section describes how to communicate and control the IQD using the DeviceNet port. DeviceNet has two basic message types: Explicit and I/O messaging.
how to get device identity information:
•
Select the service code
0E
(get attribute)
•
Select class ID
1
(select the identity object)
•
Select instance ID
1
(there is only instance supported)
•
Select attribute ID
1
(vendor ID attribute)
•
The device will respond with data bytes
64 02
meaning 264hex
or 612dec, which is the vendor ID that has been attributed to
Nor-Cal Products Inc.
•
Change the attribute ID for
6
(serial number attribute)
•
The device will respond with data bytes,
3A b1 02 00
meaning
2B13Ahex or 176442dec, which is the serial number of the device.
(Nor-Cal device serial numbers are composed of 6 digits)
how to control valve position:
•
Select the service code
10
(set attribute)
•
Select class ID
2E
(select the selection object)
•
Select instance ID
1
(setpoint)
•
Select attribute ID
5
(destination index) followed by the data
02
.
This puts the destination index to the value
2
having for effect
to select valve position control
then . . .
•
Select the service code
10
(set attribute)
•
Select class ID
2E
(select the selection object)
•
Select instance ID
1
(setpoint)
•
Select attribute ID
9
(source data value) followed by the setpoint
00 40
•
The device will move the valve to 50% of it’s stroke(45º angle)
•
Select attribute ID
9
(source data value) followed by the
setpoint
00 00
The device will move the valve to 0% of its
the stroke or closed
how to read the valve limit switch
•
Select the service code
0E
(get attribute)
•
Select class ID
8
(select the selection object)
•
Select instance ID
1
(closed limit switch)
•
Select attribute ID
3
•
The device will respond with data bytes
01
meaning that
the closed limit switch is activated and the valve is closed
•
Select instance ID
2
(open limit switch)
•
Select attribute ID
3
•
The device will respond with data bytes
00
meaning that
the open limit switch is not activated and the valve is not opened
Explicit messaging:
Explicit messages are used to read or write an individual piece of information
in the device. They are mainly used for initial configuration. Explicit messages
include the path to locate the data of interest, this consists of the class ID,
attribute ID, and instance number. They also specify an action to be taken.
The table below lists some of the key information available through explicit
messaging. Please refer to Section 9 for the full device profile characteristic.
TAbLE 8.3 - DEVICENET EXPLICIT mESSAGING
clASS
ID
InStAnce
ID
AttrIBute
ID
ActIon
vArIABle
nAme
1
1
1
0E (get)
Vendor ID
1
1
6
0E (get)
Serial Number
1
1
7
0E (get)
Product Name
3
1
1
0E (get) 10 (set)
MACID
3
1
2
0E (get) 10 (set)
Baud Rate
31
1
6
0E (get)
Process input
(CDG1)
31
2
6
0E (get)
Process input
(CDG2)
31
3
6
0E (get)
Valve position
2E
1
5
0E (get) 10 (set)
Pressure control
and position
control
2E
1
9
0E (get) 10 (set)
Process setpoint
The most straightforward way of sending individual commands to the
controller is to use a node-commissioning software utility. These utilities
are part of the DeviceNet interface card package.
Explicit messaging connection examples:
•
Power up the device, the network LED will transition to flashing green
•
Let the master open an explicit connection with the device
•
The network LED will transition to solid green
As a reminder, note that data to and from the device is always encoded least
significant byte first as specified in the data management section of the
DeviceNet protocol specification. For instance the value 12345678hex
is encoded as follow:
octet numBer
1st
2nd
3rd
4th
outPut DAtA
78
56
34
12