Page 43 of 51 | |
|
|
the control code extracted from the response and if the “DA_Byte_Name” is specified then the driver stores the count field extracted from the response.
Pattern Control Block
Object 12 variations 2 & 3 are not supported by the driver.
As a Server
The DNP 3.0Driver Server can accept and process Select and Operate commands sent by a remote Client with limitations as discussed in the notes below.
The commands can be sent to Analog Output Blocks, Relay Control Blocks and Pattern Control Blocks. The driver executes or rejects the commands on these data objects, returning a response which contains an echo of the poll with the status byte of each data object modified to report the success or failure.
The driver is intended to transfer data from one protocol to another. The driver does not make the FieldServer behave like a typical DNP 3.0 device such as a protective relay. For these reasons the driver cannot implement all the actions implied by the Select and Operate commands. For example: The driver cannot queue commands. The driver cannot use the on and off time fields. The driver only understands the ‘Latch On and “Latch Off’ command codes. The driver cannot understand the attribute bits of the control code field such as the clear and reset attribute flags.
All Commands
When one of the select, operate and direct operate commands are received, the driver sends a response which contains internal indication status bytes as well as en echo of the data objects being commanded. Each data object that can be commanded with one of the commands has a status byte field trailing the block of data sent with the object. The Server modifies the status byte that is echoed back.
The driver sends 1 of 4 possible status byte responses.
0Command Accepted
2Command rejected because object was not previously selected.
4Command rejected because the command code is not supported by the driver.
6Command Rejected, Hardware problem. The driver sends this response when the driver is not able to process the command correctly. It does not mean that the FieldServer hardware is malfunctioning.
Select Command
This command is used to select data objects for an ‘Operate’ Command. If possible the driver marks the data objects as selected when the select command is received. If not possible, the driver assumes the objects are selected at all times. Many DNP 3.0 devices implement an ‘Arm’ timer that clears the select flag when it times out. This driver does not implement this timer but relies on a remote device using another protocol to implement the ‘Arm’ timer if it so requires. The remote device can clear the select flag by writing a zero to the Data Array element at any time.
If the Server Map Descriptor used to define the Server data object to be selected/operated has the “DA_Bit_Name” parameter specified, the driver uses this Data Array location to set the select flag by setting the value to ‘1’. If the secondary Data Array is not specified then the select command is accepted and the point is considered to be permanently selected.
The driver sends responses with the status byte modified to report the success/failure of the command.
Operate Command
Once selected, data objects can be operated. If the secondary Data Array is specified using the “DA_Bit_Name” parameter, the driver looks in the Data Array and if the value is
FieldServer Technologies 1991 Tarob Court Milpitas, California 95035 USA Web: www.fieldserver.com Tel: (408) 262 2299 Fax: (408) 262 2269 Toll Free: (888) 509 1970 email: support@fieldserver.com
