Skew Calculations; Pll Feedback And Cascading Clock Network - Intel Arria 10 User Manual

3. PLLs and Clock Networks
UG-01143 | 2018.06.15
Select PMA-only bonding when a bonded protocol is not explicitly supported by the
hard PCS blocks. For example, for Interlaken protocol, PMA-only bonding is used and a
soft PCS bonding IP is implemented in the FPGA fabric.

3.9.4. Skew Calculations

To calculate the maximum skew between the channels, the following parameters are
used:
• PMA to PCS datapath interface width (S)
• Maximum difference in number of parallel clock cycles between deassertion of
each channel's FIFO reset (N).
To calculate the channel skew, the following five scenarios are considered:
• Non-bonded
In this case, both the PMA and PCS are non-bonded. Skew ranges from 0 UI to
[(S-1) + N*S] UI.
• PMA bonding using x6 / xN clock network
In this case, the PCS is non-bonded. Skew ranges from [0 to (N*S)] UI + x6/xN
clock skew.
• PMA bonding using the PLL feedback compensation clock network
In this case, the PCS is non-bonded. Skew ranges from [0 to (N*S)] UI +
(reference clock skew) + (x6 clock skew).
• PMA and PCS bonding using the x6 / xN clock network
Skew = x6 / xN clock skew.
• PMA and PCS bonding using PLL feedback compensation clock network
Skew = (reference clock skew) + (x6 clock skew).

3.10. PLL Feedback and Cascading Clock Network

The PLL feedback and cascading clock network spans the entire side of the device, and
is used for PLL feedback compensation bonding and PLL cascading.
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Intel Arria 10 Transceiver PHY User Guide
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