PCI Express
15.4.1 Differential Transmitter (Tx) Output
Table 56 defines the specifications for the differential output at all transmitters. The parameters are
specified at the component pins.
Table 56. Differential Transmitter (Tx) Output Specifications
Parameter
Unit interval
Conditions
Symbol
Min
Typical
Max
Units Notes
Each U
ppm. U
is 400 ps ± 300
UI
399.88
400
400.12
ps
1
PETX
does not account
PETX
for Spread Spectrum Clock
dictated variations.
Differential
peak-to-peak output
voltage
V
V
= 2 × |V
–
V
0.8
—
1.2
V
2
2
PEDPPTX
TX-D+
TX-DIFFp-p
|
TX-D-
De-emphasized
differential output
voltage (ratio)
Ratio of the V
second and following bits after
a transition divided by the
of the
V
–3.0
–3.5
–4.0
dB
PEDPPTX
TX-DE-RATIO
V
of the first bit after a
PEDPPTX
transition.
Minimum Tx eye width The maximum transmitter
jitter can be derived as
T
0.70
—
—
—
—
UI
UI
2, 3
2, 3
TX-EYE
T
= 1 –
TX-MAX-JITTER
U
= 0.3 UI.
PEEWTX
Maximum time between Jitter is defined as the
T
0.15
TX-EYE-MEDIAN-to-
MAX-JITTER
the jitter median and
maximum deviation
from the median
measurement variation of the
crossing points (V = 0
V) in relation to a recovered Tx
UI. A recovered Tx UI is
calculated over 3500
PEDPPTX
consecutive unit intervals of
sample data. Jitter is
measured using all edges of
the 250 consecutive UI in the
center of the 3500 UI used for
calculating the Tx UI.
D+/D– Tx output
rise/fall time
—
T
V
, T
0.125
—
—
—
—
UI
2, 5
2
TX-RISE TX-FALL
RMS AC peak common V
mode output voltage
= RMS(|V
–
V
TX-CM-ACp
20
mV
PEACPCMTX
TXD+
V
V
|/2 – V
)
TXD-
TX-CM-DC
= DC
of
TX-CM-DC
(avg)
|V
– V
|/2
TX-D+
TX-D-
Absolute delta of DC
common mode voltage V
|V
–
0
—
100
mV
2
TX-CM-DC (during LO)
TX-CM-DC- ACTIVE-
IDLE-DELTA
TX-CM-Idle-DC (During Electrical
during LO and electrical
idle
|<=100 mV
Idle)
V
= DC
of
(avg)
TX-CM-DC
|V
– V
|/2 [LO]
TX-D+
TX-D-
V
= DC
of
(avg)
TX-CM-Idle-DC
|V
– V
|/2 [Electrical
TX-D+
TX-D-
Idle]
™
MPC8378E PowerQUICC II Pro Processor Hardware Specifications, Rev. 2
66
Freescale Semiconductor
FREESCALE [ Freescale ]
