Comtech EF Data CDM-570 Installation And Operation Manual page 391

CDM-570/570L Satellite Modem with Optional IP Module
Appendix E
E.4.3.4 Instruction Code Qualifier
This single character further qualifies the preceding instruction code. Code Qualifiers obey the following rules:
1. From Controller to Target, the only permitted values are:
=
(ASCII code 61
?
(ASCII code 63)
2. From Target-to-Controller, the only permitted values are:
=
(ASCII code 61)
!
(ASCII code 33)
If the Controller sends an instruction to set a parameter to a particular value, and, if the value sent in the argument is valid, BUT the
modem will not permit that particular parameter to be changed at that time, then the Target will acknowledge the message by replying, for
example, with TFQ! (with no message arguments).
If the Controller sends an instruction code which the Target does not recognize, then the Target will acknowledge the message by echoing
the invalid instruction, followed by the ! character. Example: XYZ!
Right now the CDM software is not organized to categorize various error codes, so it combines various errors into a single code (!).
The = code is used as the assignment operator, and is used to indicate that the parameter defined by the preceding byte should be set
to the value of the argument(s) that follow it.
For example, in a message from Controller to Target, TFQ=0950.0000 would mean 'set the Transmit Frequency to 950 MHz.'
The ? code is used as the query operator, and is used to indicate that the Target should return the current value of the parameter
defined by the preceding byte.
For example, TFQ? means 'what is the current value of the Transmit Frequency?'
The = code is used in two ways:
First, if the Controller has sent a query code to a Target (for example TFQ?, meaning 'what's the Transmit frequency?'), the Target
would respond with TFQ=xxxx.xxxx, where xxxx.xxxx represents the frequency in question.
Second, if the Controller sends an instruction to set a parameter to a particular value, then, providing the value sent in the argument is
valid, the Target will acknowledge the message by replying with TFQ= (with no message arguments).
The ! code is only used as follows:
If the Controller sends an instruction code that the Target does not recognize, the Target will acknowledge the message by echoing the
invalid instruction, followed by the ! character with. Example: XYZ!
E–5
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MN/CDM570L.IOM