Setting the Maximum Skew

Versal Adaptive SoC GTY and GTYP Transceivers Architecture Manual (AM002)

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1.3 English

When the master receives a channel bonding sequence, it does not trigger channel bonding immediately. Several more bytes must arrive if the slaves have more latency. This wait time effectively becomes the maximum skew that the RX elastic buffer can handle. If the skew is greater than this wait time, the slaves might not receive the sequence by the time the master triggers channel bonding.

The figure below shows two FIFOs, one for the master and one for the slave. If the slave is behind the master, the master must wait several cycles before triggering channel bonding, otherwise the slow slave does not have the channel bonding sequence in its buffer.

Figure 1. Channel Bonding Example (Master RXCHANBONDLEVEL[2:0] = 1)

CHAN_BOND_MAX_SKEW is used to set the maximum skew allowed for channel bonding sequences 1 and 2. The maximum skew range is 1 to 14. This range must always be less than one-half the minimum distance (in bytes or 10-bit codes) between channel bonding sequences. This minimum distance is determined by the protocol being used.