Fisher-Rosemount RS3 SCI communication protocol
Supported device types and versions
Communication line configuration
Communication station configuration
I/O tag configuration
Literature
Changes and modifications
Document revisions
Supported device types and versions
The protocol supports the data transmission from/to the SCI (Supervisory Computer Interface) interface of the Fisher-Rosemount RS3 control system.
Communication line configuration
- communication line category: Serial, SerialOverUDP Device Redundant.
- Transmission parameters either 19200 or 38400 Baud (see the tab. nr. 1), 8 data bits, 1 stop bit, no parity.
For a correct communication of a Rosemount RS3 SCI device, these SCI parameters must be set:
Table 1
| Parameter | Value |
|---|---|
| Comm Port Baud Rate | 9.2 kbs or 38.4 kbs |
| Checksum | Yes |
| Data Bits and Parity | 8N |
| XON/XOFF Control | Off |
| EIA Option | None |
| Reply Header String in Hex format | 00 00 00 00 |
| Reply Trailer String in Hex format | 00 00 00 00 |
| Mode | Async Length LSB |
| Data Format | IEEE |
| TX Gap | 100 ms |
Communication station configuration
- Fisher-Rosemount RS3 SCI communication protocol.
- Address parameters require to define the parameters First index and Update
Interval.
- First index: A value within the interval 0..1499, address of the first I/O tag in the SCI table (Table Entry Location Number).
- Update interval: Time period for acquisition of new I/O tag values. Possible settings: cont. (continually), 5 sec., 10 sec., 15 sec., 30 sec., 1 min., 2 min., 5 min., 15 min. a 60 min.
SCI allows to configure acquisition of 1500 system values into its table (Table entry) with different parameters (Scaling, Update interval). Table entry are allocated to individual I/O tags from the value First index. The station represents a logic set of tags with the same Update Interval parameter. Update Interval is a time period, using of which SCI acquires new values from the Rosemount S3 system.
Note: As the SCI configuration allows to define the parameter Update Interval up to 300 seconds (5 min.), the settings is used for periods 15 and 60 minutes.
Station protocol parameters
There can be defined the following station protocol parameters:
Table 2
| Keyword | Full name | Meaning | Unit | Default value |
|---|---|---|---|---|
| RC | Retry Count | Poll repetition count in case of a communication error. | - | 2 |
| RT | Retry Timeout | Delay between poll repetition in case of a communication error. | ms | 200 |
| WFT | Wait First Timeout | Delay after transmitting the poll before reading the response. | ms | 60 |
| WT | Wait Timeout | Delay between response readings till its finalization. | ms | 200 |
| MWR | Max Wait Retry | Repetition count of response readings till its finalization. | - | 15 |
| DEBUG | Debug Mode | If the value of the parameter is YES, the tables on the side of the SCI device are not configured during communication (deletion from tables + initialization of individual points). Parameter is used only for debug purposes. | YES/NO | NO |
| SW | Send Weak | If the value is YES - if there is acquired a new I/O tag value with an error attribute, the error number will be sent to the I/O tag value and the value is marked by the WEAK attribute. It is used for debugging purposes only. | YES/NO | NO |
String containing the protocol parameters is being defined as follows:
Keyword=value;Keyword=value; ...
Example:
SW=YES;WFT=300;
If there is used a keyword with an invalid value in the initialization string, there will be used corresponding default value according the table 2.
I/O tag configuration
Possible I/O tag types: Ai, Ao, Di, Dout
Communication supports value acquisition of I/O tags of the following types:
- Analog values - I/O tag type AI,AO, used display scaling type “1”
- Discrete (binary) values - I/O tag type DI, DO, used internal scaling type “0”.
Further it allows to write new values of I/O tags of the following types:
- Analog values - I/O tag type AO, used display scaling type “1”
- Discrete (binary) values - I/O tag type DO, used internal scaling type “0”.
- Display scaling - acquired values are equal with the RS3 system displaying
- Internal scaling - discrete values are represented by : 0.0 - log. 0; 1.0 - log. 1
I/O tag address parameters
- Block Variable - is the name of the Rosemount System 3 block variable. It is being defined in form of e.g. =1E-75 for I/O tag of AI type and e.g. =1F-25/b for I/O tags of DI type.
Literature
- Rosemount System 3, PeerWay Interfaces Manual, Software Version 18, Release 1, October 1993
Changes and modifications
-
Document revisions
- Ver. 1.0 – March 5th 2001
Related pages:
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