220.127.116.11.3. Core PLL
- Link clock – from output C0
- Frame clock – from output C1
|Link Clock||Serial data rate/40||The link clock clocks the JESD204B IP core link layer and the link interface of the transport layer.|
|Frame Clock||Serial data rate/(10 × F)||The frame clock clocks the transport layer, test pattern generators and checkers, and any downstream modules in the FPGA core fabric.|
For the frame clock, when F=1 and F=2, the resulting frame clock value can easily exceed the capability of the core PLL to generate and close timing. The top level RTL file (jesd204b_ed.sv) defines the frame clock division factor parameters, F1_FRAMECLK_DIV (for cases with F = 1) and F2_FRAMECLK_DIV (for cases with F = 2). This factor enables the transport layer and test pattern generator to operate at a divided factor of the required frame clock rate by widening the data width accordingly. For this example design, the F1_FRAMECLK_DIV is set to 4 and F2_FRAMECLK_DIV is set to 2. For example, the actual frame clock for a serial data rate of 6.144 Gbps and F = 1 is:
(6144/(10 × 1)) / F1_FRAMECLK_DIV = 614.4 / 4 = 153.6 MHz
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