Quantum Composers LDDC 1550 - Manual (Page 17)

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Address
2 ASCII characters. Each device has a unique address which is
programmed into its firmware. See the table below for a list of addresses.
Deliminator
Single colon character “:”, must follow device address.
Command
String Commands are specific to each device -- see the following sections for
the commands that each device supports.
Parameters
(optional field) Some commands may have parameters which are
separated by spaces follow the command string. Multiple parameters are
also separated by spaces. To query a command parameter, append a “?”
to the end of the parameter (no space).
Terminator
ASCII carriage return character (decimal value 13). The receiving device
does not process any commands until the terminator is received.
Device Addresses
Address Device
DC Diode Controller. NOTE: Also for laser system controller
Command Types
There are two types of commands -- those that set a value or initiate an actions (control
commands), and those that request information (query commands). Each device must
respond in the proper manner to each type of command.
Control Commands
A device must always parse a control command and return a response immediately.
If the command is a recognized command and the parameter is valid, then the device returns
an "OK". ( = ASCII carriage return, decimal value 13).
If the command is not recognized by the device, then it responds with "?1
If the command is recognized, but the parameter value is missing or invalid, then the device
responds with a "?2".
If the command is recognized, but the parameter is out of range, then the device responds
with a “?3”.
If a control command is received while the device is in the midst of executing a previous
command, and the commands are mutually exclusive (cannot be executed in parallel), then the
previous command is aborted and the new one executed. It is up to the host controller (the PC) to
poll the device and make sure the previous command is finished, if that is the needed.
Query Commands
Query commands return a value to the PC as soon as the command is parsed and executed. The
value returned will depend on the command. The response is always terminated with a . If
a query command is not recognized by the device, then a "?0" is returned.