MSC8144 Freescale Semiconductor, MSC8144 Datasheet - Page 43

• Manufacturer Part Number: MSC8144
• Description: Quad Core Digital Signal Processor
• Manufacturer: Freescale Semiconductor

2.7.5.2
LP-Serial links use differential signaling. This section defines terms used in the description and specification of differential
signals. Figure 12 shows how the signals are defined. The figure shows waveforms for either a transmitter output (TD and TD)
or a receiver input (RD and RD). Each signal swings between voltage levels A and B, where A > B.
Note:
Using these waveforms, the definitions are as follows:
To illustrate these definitions using real values, consider the case of a CML (Current Mode Logic) transmitter that has a common
mode voltage of 2.25 V and each of its outputs, TD and TD, has a swing that goes between 2.5 V and 2.0 V. Using these values,
the peak-to-peak voltage swing of the signals TD and TD is 500 mV
and –500 mV. The peak differential voltage is 500 mV. The peak-to-peak differential voltage is 1000 mV
Note:
2.7.5.3
With the use of high speed serial links, the interconnect media will cause degradation of the signal at the receiver. Effects such
as Inter-Symbol Interference (ISI) or data dependent jitter are produced. This loss can be large enough to degrade the eye
opening at the receiver beyond what is allowed in the specification. To negate a portion of these effects, equalization can be
used. The most common equalization techniques that can be used are:
Freescale Semiconductor
1.
2.
3.
4.
5.
6.
•
•
A
B
This explanation uses generic TD/TD/RD/RD signal names. These correspond to SRIO_TXD/SRIO_TXD/
SRIO_RXD/SRIO_RXD respectively.
The transmitter output signals and the receiver input signals TD, TD, RD and RD each have a peak-to-peak voltage
(V
The differential output signal of the transmitter, V
The differential input signal of the receiver, V
The differential output signal of the transmitter and the differential input signal of the receiver each range from A – B
to –(A – B).
The peak value of the differential transmitter output signal and the differential receiver input signal is A – B.
The value of the differential transmitter output signal and the differential receiver input signal is 2 × (A – B) V
AC electrical specifications are given for transmitter and receiver. Long run and short run interfaces at three baud
rates (a total of six cases) are described. The parameters for the AC electrical specifications are guided by the XAUI
electrical interface specified in Clause 47 of IEEE™ Std 802.3ae-2002™. XAUI has similar application goals to
serial RapidIO. The goal of this standard is that electrical designs for serial RapidIO can reuse electrical designs for
XAUI, suitably modified for applications at the baud intervals and reaches described herein.
A passive high pass filter network placed at the receiver. This is often referred to as passive equalization.
The use of active circuits in the receiver. This is often referred to as adaptive equalization.
PP
) swing of A – B.
Signal Definitions
Equalization
TD or RD
TD or RD
MSC8144 Quad Core Digital Signal Processor Data Sheet, Rev. 1
Figure 12. Differential V
Differential Peak-Peak = 2 × (A – B)
ID
, is defined as V
OD
PP
, is defined as V
of Transmitter or Receiver
PP
. The differential output signal ranges between 500 mV
RD
– V
TD
RD
– V
.
TD
.
Electrical Characteristics
PP
.
PP
.
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