Mocomtech CDM-QX - Manual (Page 221)

CDM-Qx/QxL Multi-Channel Satellite Modem with DoubleTalk™ Carrier-in-Carrier® Revision 7
Appendix C MN/CDMQX.IOM
C–3
C.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.
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.
C.5.2 Target Address
Up to 9,999 devices can be uniquely addressed. The EIA-485 base address is set by the front
panel; the EIA-232 base address is always zero. Each plug-in Slot (as viewed from the back of the
chassis) has its own address.
Slot Address
Upper Left Base
Lower Left Base + 1
Upper Right Base + 2
Lower Right Base + 3
Common functions can be accessed through any of the four addresses. If several devices share a
RS-485 bus, it must be noted that the Qx will require four addresses, and should be spaced apart
accordingly. Empty slots in the Qx chassis still occupy an address.
A single CDM-Qx occupies four addresses. For modulator and demodulator
grouped as modem, the address will be the same as the modulator.
C.5.3 Address Delimiter
This is the character ‘/’ (forward slash) (ASCII code 47).
C.5.4 Instruction Code
This is a three-character alphabetic sequence that identifies the subject of the message. Wherever
possible, the instruction codes have been chosen to have some significance – e.g., TFQ for Tx
FreQuency; RMD for Rx 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).
C.5.5 Instruction Code Qualifier
This single character further qualifies the preceding instruction code. Code Qualifiers obey the
following rules:
IMPORTANT