Comtech EF Data CRS-200 - Manual (Page 65)

CRS-200 Redundancy Switch
Rev. 1 B–5
B.5.4 Instruction Code Qualifier
This is a single character that 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)
They have these meanings:
The ‘=’ code (controller to target) 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=070.0000 would mean ‘set the transmit frequency to 70 MHz’
The ‘?’ code (controller to target) 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’
2) From Target to Controller, the only permitted values are:
= (ASCII code 61)
? (ASCII code 63)
! (ASCII code 33)
‘
*(ASCII code 42)
They have these meanings:
The ‘=’ code (target to controller) 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=xxx.xxxx, where
xxx.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 (target to controller) 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.