902B Abs Piezo
Operation manual
12
Communication Protocol
The 902B transducer command set allows the user to change transducer parameters and receive pressure
measurements. Settings and parameters like set point values, set point configurations and calibration data
are stored in the transducers non-volatile memory.
Communication software
Communication software is required to communicate from a PC via
RS232/485 interface to the transducer. In Microsoft Windows XP package the
hyper terminal software can be used to type and transmit serial commands to
the transducer. To the right is illustrated the Windows communication port
properties for communicating with transducer factory default settings.
MKS also offers communication software examples that can be downloaded
at: www.mksinst.com/vtsw/
In OEM applications transducer communication software routines are normally
integrated with other system control software.
Query and Command Syntax
Queries return current parameter settings; commands change the parameter setting according to the value
the user enters into the command syntax. Each query or command must begin with the attention character
@ and end with the termination ;FF.
Command syntax for an information query:
@<device address><query>?;FF
Command syntax for a command:
@<device address><command>!<parameter>;FF
The command set allows upper and lower case ASCII characters.
Response Syntax (ACK/NAK)
The ASCII characters 'ACK' or 'NAK' preface the query or command response string. The ACK sequence
signifies the message was processed successfully. The NAK sequence indicates there was an error.
The response to a query or a successful command is:
@<device address>ACK<data>;FF
The response to a message with an error is:
@<device address>NAK<NAK code>;FF
Examples:
ACK response: @253ACK9600;FF (baud rate changed to 9600)
NAK response: @253NAK160;FF (command had an error—possible typo)
The following list provides descriptions of the NAK codes that may be returned.
NAK Code
Error description
Example
8
Zero adjustment at too high pressure
@253ZER!;FF
9
Atmospheric adjustment at too low pressure @253ATM!760;FF
160
Unrecognized message
@253S%;FF
169
Invalid argument
@253EN1!of;FF
172
Value out of range
@253SP1!50000000;FF
175
Command/query character invalid
@253FV!;FF
180
Not in setup mode (locked)
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