Comtech EF Data CDM-710G - Manual (Page 193)

CDM-710G High-Speed Satellite Modem Revision 1
Remote Control MN-CDM710G
A–3
A.5.1 Start Of Packet
Controller to Target: This is the character ‘<’ (ASCII code 60).
Target to Controller: This is the character ‘>’ (ASCII code 62).
Because this is used to provide a reliable indication of the start of packet, these two characters
may not appear anywhere else within the body of the message.
A.5.2 Address
Up to 9,999 devices can be uniquely addressed. In RS-232 applications this value is set to 0. In
RS-485 applications, the permissible range of values is 1 to 9999. It is programmed into a target
unit using the front panel keypad.
IMPORTANT
The controller sends a packet with the address of a target - the destination of
the packet. When the target responds, the address used is the same address,
to indicate to the controller the source of the packet. The controller does not
have its own address.
A.5.3 Instruction Code
This is a three-character alphabetic sequence which identifies the subject of the message.
Wherever possible, the instruction codes have been chosen to have some significance. For
example: TFQ for Transmit FreQuency, etc. This aids in the readability of the 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.5.4 Instruction Code Qualifier
This is a single character which 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
The = (ASCII code 61) 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’
?
(ASCII code 63)
The ? (ASCII code 63) 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’.