GS2974A Datasheet, PDF (11/16 Pages) Gennum Corporation – HD-LINX III Adaptive Cable Equalizer

does not solve this problem, since the signal to noise ratio on the circuit board could be
significantly less than the default signal detection level set by the on chip reference.
NOTE: MCLADJ is only recommended for data rates up to 360Mb/s. For data rates above
this, MCLADJ should be left floating.
4.4 Mute and Carrier Detect
The GS2974A includes a MUTE input pin that allows the application interface to mute the
serial digital output at any time. Set the MUTE pin HIGH to mute SDO and SDO. In this
case, the outputs will mute regardless of the setting of the BYPASS pin.
A Carrier Detect output pin (CD) indicates the presence of a valid signal at the input of
the GS2974A. When CD is LOW, the device has detected a valid input on SDI and SDI.
When CD is HIGH, the device has not detected a valid input.
NOTE: This pin may be connected directly to the CD pin to allow mute on loss of carrier.
NOTE: CD will only detect loss of carrier for data rates greater than 19Mb/s. The CD
output pin may be connected directly to the MUTE input pin to enable automatic muting
of the GS2974A when no valid input signal has been detected.
NOTE: If the maximum cable length is exceeded and the device is not in bypass mode
the GS2974A will not assert the CD pin even if a carrier is present.
Table 4-1: Mute Input Table
Mute
0
1
Function
SDO and SDO operate normally
SDO and SDO are forced to a steady
state
Table 4-2: CD Output Table
CD
0
1
Input Status
Valid Input on SDI, SDI pins
Input is not valid
GS2974A HD-LINX™ III Adaptive Cable Equalizer
Data Sheet
42216 - 3
January 2009
11 of 16