Programming Guide
9 Programming Guide
This section explains the sensor’s communication protocol. Use them when writing custom programs for your applications or when communicating with your sensor with a terminal program.
9.1 Remote versus Manual Considerations
Since the sensor includes a local user interface, the possibility exists for a person to make manual changes to parameter settings. To resolve conflicts between inputs to the sensor, it observes the following rules:
•Command precedence: the most recent parameter change is valid, whether originating from manual or remote.
•If a manual parameter change is made, the sensor will transmit a “notification” string to the host. (Notification strings are suppressed in multidrop mode.)
•A manual lockout command is available in the protocols set so the host can render the user interface “display only,” if desired.
All parameters set via the 2‐way interface are retained in the sensor’s nonvolatile memory.
When a unit is placed in multidrop mode its manual user interface is automatically locked! It can be unlocked with the command XXXJ=U <CR>, where XXX is the multidrop address.
9.2 Command Structure
Protocols are the set of commands that define all possible communications with the sensor. The commands are described in the following sections along with their associated ASCII command characters and related message format information. Types of commands include the following:
1.A request for the current value of a parameter
2.A change in the setting of a parameter
3.Defining the information contents of a string (either continuously output or periodically polled at the option of the user)
The sensor will respond to every command with either an “acknowledge” or a “not acknowledge” string. Acknowledge strings begin with the exclamation mark ! and are either verification of a set command or a parameter value. If the unit is in multidrop mode the 3‐digit address can be sent out before the exclamation mark.
For a change in the setting of a parameter, the range of possible setting values is defined, and, if the host inputs a value outside the allowed range, an appropriate “error” response character shall be transmitted back by the sensor.
All commands must be entered in upper case (capital) letters. Also note that leading and trailing zeros are necessary!
Marathon Series FA/FR | 39 |