System Design Information
21.10 Guidelines for High-Speed Interface Termination
This section provides the guidelines for high-speed interface termination when the SerDes interface is
entirely unused and when it is partly unused.
21.10.1 SerDes Interface Entirely Unused
If the high-speed SerDes interface is not used at all, the unused pin should be terminated as described in
this section.
The following pins must be left unconnected (float):
•
•
•
SD_TX[7:0]
SD_TX[7:0]
Reserved pins T22, T23, M20, M21
The following pins must be connected to GND:
•
•
•
•
SD_RX[7:0]
SD_RX[7:0]
SD_REF_CLK
SD_REF_CLK
NOTE
It is recommended to power down the unused lane through SRDSCR1[0:7]
register (offset = 0xE_0F08) (This prevents the oscillations and holds the
receiver output in a fixed state.) that maps to SERDES lane 0 to lane 7
accordingly.
Pins V28 and M26 must be tied to XV . Pins V27 and M25 must be tied to GND through a 300-Ω
DD
resistor.
In Rev 2.0 silicon, POR configuration pin cfg_srds_en on TSEC4_TXD[2]/TSEC3_TXD[6] can be used
to power down SerDes block.
21.10.2 SerDes Interface Partly Unused
If only part of the high-speed SerDes interface pins are used, the remaining high-speed serial I/O pins
should be terminated as described in this section.
The following pins must be left unconnected (float) if not used:
•
•
•
SD_TX[7:0]
SD_TX[7:0]
Reserved pins: T22, T23, M20, M21
The following pins must be connected to GND if not used:
•
•
•
SD_RX[7:0]
SD_RX[7:0]
SD_REF_CLK
MPC8548E PowerQUICC™ III Integrated Processor Hardware Specifications, Rev. 6
Freescale Semiconductor
136
FREESCALE [ Freescale ]
