Comtech EF Data CDM-625A, Installation And Operation Manual

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CDM-625A Advanced Satellite Modem MN-CDM625A
Serial-based Remote Product Management Revision 4
8–4
8.4.1.1 Start of Packet
•
Controller-to-Target: This is the character ‘<’ (ASCII code 60).
•
Target-to-Controller: This is the character ‘>’ (ASCII code 62).
The ‘ < ’ and ‘ > ’ characters indicate the start of packet. They may not appear anywhere else within the body of the message.
8.4.1.2 Target Address
Up to 9999 devices can be uniquely addressed. In EIA-232 applications this value is set to 0. In EIA-485 applications, the permissible
range of values is 1 to 9999. It is programmed into a Target unit using the front panel keypad.
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.
8.4.1.3 Address Delimiter
This is the “forward slash” character ' / ' (ASCII code 47).
8.4.1.4 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 – e.g.,
TFQ
for transmit frequency,
RMD
for receive modulation type, 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).