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CDM-740 Advanced Satellite Modem
Remote Control
message, should it be displayed in its raw ASCII form. Only upper case alphabetic characters
may be used (A-Z, ASCII codes 65 - 90).
A.4.5
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 63)
!
(ASCII code 33)
*
(ASCII code 42)
#
(ASCII code 35)
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=0070.0000 would mean 'set the Transmit frequency to 70 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: In a message from Controller-to-Target, TFQ? would mean
'return 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 is 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 to set a parameter to a particular value,
then, if the value sent in the argument is not valid, the Target will acknowledge
the message by replying, for example, with TFQ? (with no message
Arguments). This indicates that there was an error in the message sent by the
Controller.
The ! code is only used as follows:
If the Controller sends an instruction code which the Target does not recognize,
the Target will acknowledge the message by echoing the invalid instruction,
followed by the ! character. Example: XYZ!
The * code is only used as follows:
If the Controller sends an instruction to set a parameter to a particular value,
then, if the value sent in the argument is valid, BUT the modem will not permit
that particular parameter to be changed at that time, the Target will
acknowledge the message by replying, for example, with TFQ* (with no
message Arguments).
The # code is only used as follows:
If the Controller sends a correctly formatted command, BUT the modem is not in
remote mode, it will not allow reconfiguration, and will respond with TFQ#.
A–3
Revision 0
MN-CDM740
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