Design considerations, Design considerations -1 – Altera Triple Speed Ethernet MegaCore Function User Manual
Page 163
8
Design Considerations
2014.06.30
UG-01008
Optimizing Clock Resources in Multiport MAC with PCS and Embedded PMA
The following factors determine the total number of global and regional clock resources required by your
system:
• Configuration of the Triple-Speed Ethernet MegaCore function and the blocks it contains
• PCS operating mode (SGMII or 1000BASE-X)
• PMA technology implemented in the target device
• Number of clocks that can share a single source
• Number of PMAs required in the design
• ALTGX megafunction operating mode
You can use the same clock source to drive clocks that are visible at the top-level design, thus reducing the
total number of clock sources required by the entire design.
Table 8-1: Clock Signals Visible at Top-Level Design
Clock and reset signals that are visible at the top-level design for each possible configuration.
Clocks
MAC and PCS with PMA
MAC and PCS
MAC Only
Yes
—
—
rx_recovclkout
Yes
—
—
ref_clk
Yes
Yes
Yes
clk
Yes
Yes
Yes
ff_tx_clk
Yes
Yes
Yes
ff_rx_clk
No
No
Yes
tx_clk
No
No
Yes
rx_clk
No
Yes
—
tbi_rx_clk
No
Yes
—
tbi_tx_clk
Yes
—
—
Yes
—
—
reconfig_clk
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