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Cheetah NS SAS Product Manual, Rev. B
57
9.5.2.1.2 Receive eye mask
Figure 30 describes the receive eye mask. This eye mask applies to jitter after the application of a single pole
high-pass frequency-weighting function that progressively attenuates jitter at 20 dB/decade below a frequency
of ((bit rate) / 1.667).
Figure 30. Receive eye mask
Verifying compliance with the limits represented by the receive eye mask should be done with reverse channel
traffic present in order that the effects of crosstalk are taken into account.
9.5.2.1.3 Jitter tolerance masks
Figure 31 describes the receive tolerance eye masks and is constructed using the X2 and Z2 values given in
table 16. X1
OP
is half the value for total jitter intable 16 and X1
TOL
is half the value for total jitter in table 17, for
jitter frequencies above ((bit rate) / 1.667).
Figure 31. Receive tolerance eye mask
Absolute
amplitude
(in V)
Z1
Z2
0 V
-Z1
-Z2
X1X2
1-X2
1-X1
Normalized time (in UI)
01
Absolute
amplitude
(in V)
Z1
TOL
0 V
-Z1
OP
X1
OP
X2
1-X1
TOL
1-X1
OP
Normalized time (in UI)
(additional sinusoidal jitter) / 2
-Z1
TOL
Z1
OP
X1
TOL
Outline of eye mask
after adding
sinusoidal jitter
Outline of eye mask
before adding
sinusoidal jitter
01
Z2
-Z2