IDT80KSW0002 Datasheet
CPS-16 Datasheet 47 April 6, 2016
Signal Definitions
LP-Serial links uses differential signaling. This section defines terms used in the description and specification of differential signals. Differential Peak-
Peak Voltage of Transmitter or Receiver 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 A Volts and B Volts where A > B. Using these waveforms, the definitions are as follows:
1. The transmitter output signals and the receiver input signals TD, TD
, RD and RD each have a peak-to-peak swing of A - B Volts
2. The differential output signal of the transmitter, V
OD
, is defined as V
TD
-V
TD
.
3. The differential input signal of the receiver, V
ID
, is defined as V
RD
-V
RD
.
4. The differential output signal of the transmitter and the differential input signal of the receiver each range from A - B to -(A - B) Volts.
5. The peak value of the differential transmitter output signal and the differential receiver input signal is A - B Volts
6. The peak-to-peak value of the differential transmitter output signal and the differential receiver input signal is 2 * (A - B) Volts
Figure 14 Differential Peak-Peak Voltage of Transmitter or Receiver
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 2.5V and 2.0V. Using these values, the peak-to-peak voltage swing of the
signals TD and TD
is 500 mV p-p. The differential output signal ranges between 500 mV and -500 mV. The peak differential voltage is 500 mV. The
peak-to-peak differential voltage is 1000 mV p-p.
Equalization
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 equalization technique implemented in the CPS-16 is
Pre-emphasis on the transmitter (under register control).
Explanatory Note on Transmitter and Receiver Specifications
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 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.
Transmitter Specifications
LP-Serial transmitter electrical and timing specifications are stated in the text and tables of this section.
A Volts
B Volts
TD or RD
TD or RD
Differential Peak-Peak = 2 * (A – B)
