GX4002 Datasheet, PDF (27/74 Pages) Gennum Corporation – Dynamic on-chip power management control

3.5 Status Indicators
The GX4002 supports three status indicators: Loss of Signal (LOS), Loss of Lock (LOL) and
Channel 0 Fault (Ch0FAULT). LOS and LOL indicators are available on both the Ch1 and
the Ch0 paths.
3.5.1 Ch0 Loss Of Signal (LOS)
The Ch0 LOS indicator status is available through a register. If desired, its status can be
included in the generation of the Ch0FAULT output pin. The LOS assert threshold can be
set from 20mV to 100mV in <1mV steps. In addition, the temperature coefficient of the
LOS threshold can be adjusted to ensure consistent LOS operation over temperature.
The LOS also has hysteresis that is programmable from 0dB to 6dB in steps of 0.5dB.
The following registers are used to control the Ch0 LOS feature:
Register Name
CH0_REG9
CH0_REG10
CH0_REG11
CH0_REG12
Register
Address^d
39
40
41
42
Parameter Name
CH0LOSTHNEG
CH0LOSTHPOS
CH0LOSHYS
CH0LOSSOFTASSERT
CH0LOSSOFTASSERTEN
Bit
Position
Access
7:0
RW
7:0
RW
3:0
RW
3:3
RW
4:4
RW
Reset Value^b
01010011
00000000
1001
0
0
Valid
Range^d
Function
0-255
0-255
0-15
0-1
0-1
Negative temperature coefficient LOS
threshold setting.
Positive temperature coefficient LOS
threshold setting.
Sets LOS hysteresis from 0dB to 6dB in steps
of 0.5dB.
When HIGH, asserts LOS for internal
functions, asserts LOS register (CH0PLLLOS)
and asserts external indication through
Ch0FAULT.
When HIGH, LOS is controlled by
CH0LOSSOFTASSERT.
3.5.1.1 Ch0 LOS Threshold
Figure 3-10 and Figure 3-11 show the typical recommended range of Ch0 LOS assert
thresholds and corresponding CH0LOSTHNEG[7:0] setting to achieve these thresholds.
It is recommended to keep CH0LOSPOS[7:0] = 0 to achieve a flat temperature
coefficient for LOS threshold. The Ch0 LOS de-assert thresholds are the same as the Ch0
LOS assert thresholds for a hysteresis setting of 0.
GX4002 2x2 14.025Gb/s Crosspoint Switch with Trace
Equalization and Output De-Emphasis
Data Sheet
55972 - 0
March 2012
27 of 74
Proprietary & Confidential