mpc8378 Freescale Semiconductor, Inc, mpc8378 Datasheet - Page 82

• Manufacturer Part Number: mpc8378
• Description: Powerquicc Ii Pro Processor
• Manufacturer: Freescale Semiconductor, Inc

High-Speed Serial Interfaces (HSSI)
82
•
SD n _REF_CLK
SD n _REF_CLK
— For external DC-coupled connection, as described in
— For external AC-coupled connection, there is no common mode voltage requirement for the
Single-ended Mode
— The reference clock can also be single-ended. The SD _REF_CLK input amplitude
— The SDn_REF_CLK input average voltage must be between 200 mV and 400 mV.
— To meet the input amplitude requirement, the reference clock inputs might need to be DC or
Figure 53. Differential Reference Clock Input DC Requirements (External DC-Coupled)
greater than 200 mV. This requirement is the same for both external DC-coupled or
AC-coupled connection.
Clock Receiver
requirement for average voltage (common mode voltage) to be between 100 mV and 400 mV.
Figure 53
scheme.
clock driver. Since the external AC-coupling capacitor blocks the DC level, the clock driver
and the SerDes reference clock receiver operate in different command mode voltages. The
SerDes reference clock receiver in this connection scheme has its common mode voltage set to
SGND_SRDSn. Each signal wire of the differential inputs is allowed to swing below and above
the command mode voltage (SGND_SRDSn).
input requirement for AC-coupled connection scheme.
(single-ended swing) must be between 400 mV and 800 mV
SDn_REF_CLK either left unconnected or tied to ground.
shows the SerDes reference clock input requirement for single-ended signaling mode.
AC-coupled externally. For the best noise performance, the reference of the clock could be DC
or AC-coupled into the unused phase (SDn_REF_CLK) through the same source impedance as
the clock input (SDn_REF_CLK) in use.
MPC8377E PowerQUICC II Pro Processor Hardware Specifications, Rev. 3
shows the SerDes reference clock input requirement for DC-coupled connection
Characteristics,” the maximum average current requirements sets the
200 mV < Input Amplitude or Differential Peak < 800 mV
Figure 54
Section 21.2.1, “SerDes Reference
shows the SerDes reference clock
p-p
(from V
100 mV < V
min
Freescale Semiconductor
to V
V
max
cm
max
V
< 800 mV
< 400 mV
min
) with
Figure 55
> 0 V