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OPERATION
D395-90-880 Issue E
4.6 RS232 operation (enhanced only)
4.6.1 Message basics
The communications to the ADC work on a master / slave principle. The ADC is the slave and will only transmit a
message in response to one sent to it. The master, a PC for example, must always start the conversation.
A conversation consists of a message to the ADC and it's response back. Having sent a message to the ADC, wait for
the reply before continuing. When the ADC receives a message a reply is always sent. If the message cannot be
understood or if the syntax is wrong, an error message of the form "Err n" will be returned. Refer to Appendix A for
a list of error numbers.
All messages consist of ASCII coded characters. Messages to the ADC start with either a "!" or a "?" character. All
messages end with a carriage return (cr). Characters not enclosed by start (!?) and end (cr) characters will be ignored.
Incomplete messages will be ignored if a new start character is received. Responses from the ADC end with a carriage
return (cr).
There are two basic types of message sent to the ADC:
z Commands sending information to the ADC (starting with "!").
z Queries requesting information from the ADC (starting with "?").
4.6.2 Commands
Commands send information to the ADC. These can be literal commands such as 'turn gauge on' or values to be stored
by the ADC such as 'set-point 1 high threshold'. A summary of available commands is shown in Table 9. Full details of
the commands are given in Appendix B.
4.6.3 Queries
Queries request information from the ADC. These can be direct queries of the value of a parameter such as gauge
pressure, or reading a value currently stored in the ADC. A summary of available queries is shown in Tab le 10 . Full
details of the queries and the corresponding response from the ADC are given in Appendix C.
WARNING
The data received from this unit should not be used for safety purposes.
Table 9 - RS232 commands
Mnemonic Meaning
!CH Set-point high threshold
!CL Set-point low threshold
!GA Accept gauge error
!GW Switch gauge on/off
!RC Relay controlling gauge
!TH Link high threshold
!TL Link low threshold
!US Units
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