Related Information
Clock Correlation
on page 4-23
Clock Correlation
This section describes the clock correlation between the device clock, link clock, frame clock, and local
multi-frame clock.
Example 1
Targeted device with LMF=222, K=16 and Data rate = 6.5 Gbps
Device Clock selected = 325 MHz (obtained during IP core generation)
Link Clock = 6.5 GHz/40 = 162.5 MHz Frame Clock = 6.5 GHz/(10x2) = 325 MHz
Local Multi-frame clock = 325 MHz / 16 = 20.3125 MHz
SYSREF Frequency = Local Multi-frame Clock / n; (n = integer; 1, 2, …)
Local multi-frame clock counter = (F × K/4) = (2×16/4) = 8 link clocks
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Example 2
Targeted device with LMF=244, K=16 and Data rate = 5.0 Gbps
Device Clock selected = 125 MHz (obtained during IP core generation)
Link Clock = 5 GHz/40 = 125 MHz
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Frame Clock = 5 GHz /(10×4) = 125 MHz
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Local Multi-frame clock = 125 MHz / 16 = 7.8125 MHz
SYSREF Frequency = Local Multi-frame Clock / n; (n = integer; 1, 2, …)
Local multi-frame clock counter = (F × K/4) = (4×8/4) = 8 link clocks
(18)
Example 3
Targeted device with LMF=421, K=32 and Data rate = 10.0 Gbps
Device Clock selected = 250 MHz (obtained during IP core generation)
Link Clock = 10 GHz/40 = 250 MHz
Frame Clock = 10 GHz/(10×1) = 1 GHz
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Local Multi-frame clock = 1 GHz / 32 = 31.25 MHz
SYSREF Frequency = Local Multi-frame Clock / n; (n = integer; 1, 2, …)
Local multi-frame clock counter = (F × K/4) = (1×32/4) = 8 link clocks
(18)
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Eight link clocks means that the local multi-frame clock counts from value 0 to 7 and then loopback to 0.
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The link clock and frame clock are running at the same frequency. You only need to generate one clock from
the Altera PLL or Altera IO PLL IP core.
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For this example, the frame clock may not be able to run up to 1 GHz in the FPGA fabric. The JESD204B
transport layer in the design example supports running the data stream of half rate (1 GHz/2 = 500 MHz), at
two times the data bus width or of quarter rate (1GHz/4 = 250MHz), at four times the data bus width.
UG-01142
2015.05.04
Clock Correlation
4-23
JESD204B IP Core Functional Description
Altera Corporation
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