Chapter 8: Downstream Cable Access Modules (DCAMs)
STANDARD Revision 1.0
C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved.
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Primary Software Function
The primary software functions of the XD CAM include:
Packetization, queueing, and scheduling of all downstream packets
Downstream channel bonding of flows
Creation of DOCSIS downstream SYNC messages
Combining the digital representation of up to eight single channels into a single wideband channel, suitable for
upconversion
Conversion of the wideband digital signal into an analog signal and placement of this at a selected point in the CATV RF
spectrum
Support of a configurable modulation type (64QAM and 256QAM) per RF block upconverter
Support for interleaver depth selection on a per F-connector basis (This applies to Annex B only: Annex A has a fixed
interleaver.)
Support of independent adjustment of RF power on a per block upconverter basis
Support of the individual muting of channels within an RF block upconverter group to -50dBc
Automatic Gain Control (AGC) is always enabled on the XD CAM.
Downstream Test Port on XD CAM Faceplate
The test port on the XD CAM faceplate is meant to verify the presence of a downstream signal. It provides a power level
that is approximately 30 dB less than the configured downstream signal strength. This test port is not meant to be used for
signal calibration, detecting signal spurs, or to be used for precise RF quality measurements. When the test port is not in
use, a 75 Ohm terminator should be in place.
A single RF test port is located on the XD CAM front panel. An LED is lit to reflect which of the four upconverters is
selected. These four LEDs on an XD CAM are labeled Port 0, Port 1, Port 2 and Port 3 (or D 0-3, D 4-7, D 8-11 and D 12-15
on a 16D CAM front panel which has been upgraded to an XD CAM).