MPC8315E-RDBA Freescale Semiconductor, MPC8315E-RDBA Datasheet - Page 54

• Manufacturer Part Number: MPC8315E-RDBA
• Description: BOARD MPU 8315 POWERQUICC II
• Manufacturer: Freescale Semiconductor
• Series: PowerQUICC II™ PROr
• Type: MPUr

Specifications of MPC8315E-RDBA

• Contents: Board
• Processor To Be Evaluated: MPC8315E
• Data Bus Width: 32 bit
• Interface Type: Ethernet, I2C, SPI, UART
• Operating Supply Voltage: 1.8 V
• For Use With/related Products: MPC8315E
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

High-Speed Serial Interfaces (HSSI)
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 each signal (TD
or TD) is 500 mV p-p, which is referred as the single-ended swing for each signal. In this example, since
the differential signaling environment is fully symmetrical, the transmitter output’s differential swing
(V
54
OD
5. Differential Peak-to-Peak, V
6. Differential Waveform
7. Common Mode Voltage, V
) has the same amplitude as each signal’s single-ended swing. The differential output signal ranges
The peak value of the differential transmitter output signal or the differential receiver input signal
is defined as Differential Peak Voltage, V
Because the differential output signal of the transmitter and the differential input signal of the
receiver each range from A – B to –(A – B) Volts, the peak-to-peak value of the differential
transmitter output signal or the differential receiver input signal is defined as Differential
Peak-to-Peak Voltage, V
swing in amplitude, or twice of the differential peak. For example, the output differential peak-peak
voltage can also be calculated as V
The differential waveform is constructed by subtracting the inverting signal (TXn, for example)
from the non-inverting signal (TXn, for example) within a differential pair. There is only one signal
trace curve in a differential waveform. The voltage represented in the differential waveform is not
referenced to ground. Refer to
The Common Mode Voltage is equal to one half of the sum of the voltages between each conductor
of a balanced interchange circuit and ground. In this example, for SerDes output, V
+ V
within a differential pair. In a system, the common mode voltage may often differ from one
component’s output to the other’s input. Sometimes, it may be even different between the receiver
input and driver output circuits within the same component. It’s also referred as the DC offset in
some occasion.
A Volts
B Volts
TXn
)/2 = (A + B) / 2, which is the arithmetic mean of the two complimentary output voltages
Figure 38. Differential Voltage Definitions for Transmitter or Receiver
MPC8315E PowerQUICC
TXn or RXn
TXn or RXn
DIFFp-p
Differential Peak-Peak Voltage, V
cm
DIFFp-p
Figure 47
= 2*V
™
TX-DIFFp-p
II Pro Processor Hardware Specifications, Rev. 0
Differential Swing, V
Differential Peak Voltage, V
DIFFp
as an example for differential waveform.
DIFFp
= 2 * |(A - B)| Volts, which is twice of differential
= 2*|V
= |A – B| Volts.
OD
ID
or V
DIFFpp
|.
OD
DIFFp
= 2*V
= A - B
= |A - B|
DIFFp
(not shown)
Freescale Semiconductor
V
cm
= (A + B) / 2
cm_out
= (V
TXn