Input Clocks
4.5
Platform to FIFO Restrictions
Please note the following FIFO maximum speed restrictions based on platform speed.
For FIFO GMII mode:
FIFO TX/RX clock frequency ≤ platform clock frequency/4.2
For example, if the platform frequency is 533 MHz, the FIFO TX/RX clock frequency should be no more
than 127 MHz
For FIFO encoded mode:
FIFO TX/RX clock frequency ≤ platform clock frequency/4.2
For example, if the platform frequency is 533 MHz, the FIFO TX/RX clock frequency should be no more
than 167 MHz.
4.6
Platform Frequency Requirements for PCI-Express and Serial
RapidIO
The CCB clock frequency must be considered for proper operation of the high-speed PCI-Express and
Serial RapidIO interfaces as described below.
For proper PCI Express operation, the CCB clock frequency must be greater than:
527 MHz × (PCI-Express link width)
8
See MPC8548ERM, Rev. 2, PowerQUICC™ III Integrated Processor Family Reference Manual,
Section 18.1.3.2, “Link Width,” for PCI Express interface width details.
For proper serial RapidIO operation, the CCB clock frequency must be greater than:
2 × (0.80) × (Serial RapidIO interface frequency) × (Serial RapidIO link width)
64
See MPC8548ERM, Rev. 2, PowerQUICC™ III Integrated Processor Family Reference Manual,
Section 17.4, “1x/4x LP-Serial Signal Descriptions,” for serial RapidIO interface width and frequency
details.
4.7
Other Input Clocks
For information on the input clocks of other functional blocks of the platform see the specific section of
this document.
MPC8548E PowerQUICC™ III Integrated Processor Hardware Specifications, Rev. 6
Freescale Semiconductor
17
FREESCALE [ Freescale ]
