XENTRA 4900 communication protocol
Supported device types and versions
Communication supports reading data from Servomex XENTRA 4900 devices.
Communication line configuration
Required communication line parameters:
- Communication line category: Serial.
- Baud rate of 2400,4800,9600 or 19200 Bd - according to the device settings.
- Number of stop bits - according to the device settings.
- Number of data bits - according to the device settings.
- Parity - according to the device settings.
Other parameters, see the topic Communication line - configuration dialog box.
Communication station configuration
- Communication protocol: Servomex XENTRA.
- Station address is not used (one XENTRA device is being connected on the line)
Station protocol parameters
The following station protocol parameters can be defined:
|Keyword||Full name||Meaning||Unit||Default value|
|WT||Wait Timeout||Delay between individual line readings.||ms||1000|
|MWR||Max Wait Retry||Repetition count of line readings when the message is not completed yet.||-||15|
|XT||XENTRA Time||I/O tag value time allocated from received message (YES) or from PC (NO).||YES/NO||NO|
|SC||START CODE||Transmitted string containing object values (data frame) begins with the binary code of 0x01 (start code). Setting the parameter to NO disables searching for the start code. The setting is required by newer versions of the XENTRA device firmware.||YES/NO||YES|
String containing the protocol parameters is being defined as follows:
If there is used a keyword with an invalid value in the initialization string, there will be used corresponding default value according the table 1.
I/O tag configuration
Possible I/O tag types: Ai (Analog Input) or TiA (Absolute Time Input).
Example of received data message:
14-07-97;16:15:32;06; O2 ; 20.95; % ; CO ; 6.2;vpm; NO ; 3.5;vpm; NOx ; 0.2;vpm;||||||; 0.0; mA;||||||; 0.0; mA;1EBF;
From the message format implies, that individual items are semi-colon separated (;) - it defines I/O tag addressing. In the tab Address of the I/O tag configuration dialog box, there is required one number - item index in the data packet. Index is defined as a decimal number from 1. It means that the index of 1 contains the item 14-07-97, the index of 5 contains the item 20.95, the index of 8 contains the item 6.2, etc.
Ai type: there can be used just the indexes (addresses) of I/O tags, which can be converted to a real number. In the example above: indexes (addresses) of 3,5,8,11,14,17 and 20 (their values are: 6.0, 20.95, 6.2, 3.5, 0.2, 0.0 and 0.0). If the item can't be converted to a real number, the I/O tag value is invalid.
TiA type: there can be configured only one I/O tag of TiA type - the index (address) of 0. The I/O tag get the time and date from the items of the indexes of 1 and 2. In the example above - it is the value of 16:15:32 14-07-1997.
I/O tag value time
Times of new values of I/O tags can be:
- acquired from the data packet (identical with the value the I/O tag of TIA 0)
- real time of the PC, when the value was assigned to.
One of the options is being defined by means of the station protocol parameter XT (see the table 1).
Changes and modification
- Ver. 1.2 – February 8th, 2000 – update of 4.07 and 4.10 versions
- Ver. 1.3 - April 12th, 2002 - the protocol parameters SC added