MSC8156 Freescale Semiconductor, Inc, MSC8156 Datasheet - Page 42

• Manufacturer Part Number: MSC8156
• Description: Six-core Digital Signal Processor
• Manufacturer: Freescale Semiconductor, Inc

Electrical Characteristics
2.6.2.2
The AC requirements for PCI Express implementations have separate requirements for the Tx and Rx lines. The MSC8156
supports a 2.5 Gbps PCI Express interface defined by the PCI Express Base Specification, Revision 1.0a. The transmitter
specifications are defined in
the component pins. the AC timing specifications do not include REF_CLK jitter.
Note:
42
Unit interval
Minimum Tx eye width
Maximum time between the jitter median and
maximum deviation from the median.
AC coupling capacitor
Notes:
Unit Interval
Minimum receiver eye width
Maximum time between the jitter median
and maximum deviation from the median.
Notes:
Specifications are valid at the recommended operating conditions listed in
1.
2.
3.
4.
5.
1.
2.
3.
4.
5.
Table 25. PCI Express (2.5 Gbps) Differential Transmitter (Tx) Output AC Specifications
Table 26. PCI Express (2.5 Gbps) Differential Receiver (Rx) Input AC Specifications
Each UI is 400 ps ± 300 ppm. UI does not account for spread spectrum clock dictated variations. No test load is necessarily
associated with this value.
The maximum transmitter jitter can be derived as T
Specified at the measurement point into a timing and voltage compliance test load as shown in
any 250 consecutive Tx UIs. A T
T
median is less than half of the total Tx jitter budget collected over any 250 consecutive Tx UIs. It should be noted that the
median is not the same as the mean. The jitter median describes the point in time where the number of jitter points on either
side is approximately equal as opposed to the averaged time value. Jitter is defined as the measurement variation of the
crossing points (V
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.
All transmitters shall be AC-coupled. The AC coupling is required either within the media or within the transmitting component
itself. The SerDes transmitter does not have built-in Tx capacitance. An external AC coupling capacitor is required.
Each UI is 400 ps ± 300 ppm. UI does not account for spread spectrum clock dictated variations. No test load is necessarily
associated with this value.
The maximum interconnect media and transmitter jitter that can be tolerated by the receiver can be derived as
T
Specified at the measurement point and measured over any 250 consecutive UIs. The test load in
the Rx device when taking measurements. If the clocks to the Rx and Tx are not derived from the same reference clock, the
Tx UI recovered from 3500 consecutive UI must be used as a reference for the eye diagram.
A T
interconnect collected any 250 consecutive UIs. The T
which the median and the maximum deviation from the median is less than half of the total. UI jitter budget collected over any
250 consecutive Tx UIs. It should be noted that the median is not the same as the mean. The jitter median describes the point
in time where the number of jitter points on either side is approximately equal as opposed to the averaged time value. If the
clocks to the Rx and Tx are not derived from the same reference clock, the Tx UI recovered from 3500 consecutive UI must
be used as the reference for the eye diagram.
Jitter is defined as the measurement variation of the crossing points (V
recovered Tx UI is calculated over 3500 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. It is recommended that the recovered Tx UI is
calculated using all edges in the 3500 consecutive UI interval with a fit algorithm using a minimization merit function. Least
squares and median deviation fits have worked well with experimental and simulated data.
Parameter
TX-JITTER-MAX
RX-MAX-JITTER
PCI Express AC Physical Layer Specifications
Parameter
RX-EYE
= 0.40 UI provides for a total sum of 0.60 UI deterministic and random jitter budget for the transmitter and
= 0.30 UI for the transmitter collected over any 250 consecutive Tx UIs. The T
Table 25
= 1 – T
MSC8156 Six-Core Digital Signal Processor Data Sheet, Rev. 1
TX-DIFFp-p
RX-EYE
and the receiver specifications are defined in
= 0 V) in relation to a recovered Tx UI. A recovered Tx UI is calculated over 3500 consecutive
= 0.6 UI.
T
RX-EYE-MEDIAN-to-MAX
TX-EYE
T
TX-EYE-MEDIAN-
Symbol
T
to-MAX-JITTER
-JITTER
RX-EYE
= 0.70 UI provides for a total sum of deterministic and random jitter budget of
Symbol
T
UI
TX-EYE
C
UI
TX
TX-MAX-JITTER
RX-EYE-MEDIAN-to-MAX-JITTER
399.88
399.88
0.70
Min
Min
0.4
75
—
—
= 1 – T
RX-DIFFp-p
TX-EYE
Typical
Typical
400.00
400.00
—
—
—
—
—
Table
Table
= 0.3 UI.
= 0 V) in relation to a recovered Tx UI. A
specification ensures a jitter distribution in
26. The parameters are specified at
3.
400.12
400.12
Max
0.15
Max
200
0.3
—
—
TX-EYE-MEDIAN-to-MAX-JITTER
Figure 8
Figure 8
Freescale Semiconductor
and measured over
Units
Units
should be used as
nF
ps
UI
UI
ps
UI
UI
Notes
Notes
2, 3, 4
3, 4, 5
2, 3
3, 4
1
5
1