A low latency datapath bypasses much of the standard PCS, allowing more design control in the FPGA fabric. Use the Low Latency PHY IP to enable the standard PCS in a low latency datapath.
To implement a Low Latency PHY link, instantiate the Low Latency PHY IP in the IP Catalog, under Transceiver PHY in the Interfaces menu. In the Low Latency GUI under the General tab, select Standard on the Datapath type field.
The standard PCS can be used in a low latency datapath that contains only the following blocks:
- Phase compensation FIFO
- Byte serializer and deserializer
Figure 208. Standard PCS Low Latency Datapath
You can divide the low latency datapath into two configurations based on the FPGA fabric-transceiver interface width and the PMA-PCS interface width (serialization factor):
- Low latency 8/10-bit-width—the PCS-PMA interface width is in 8-bit or 10-bit mode for lower data rates.
- Low latency 16/20-bit-width—the PCS-PMA interface width is in 16-bit or 20-bit mode for higher data rates.
Table 84. PCS-PMA Interface Widths and Data Rates
Low Latency PHY IP Core |
Supported Data Rate Range PMA |
Low Latency 8-bit width |
600 Mbps to 4.24 Gbps |
Low Latency 10-bit width |
600 Mbps to 5.30 Gbps |
Low Latency 16-bit width |
600 Mbps to 7.84 Gbps |
Low Latency 20-bit width |
600 Mbps to 9.80 Gbps |
In the low latency datapath, the TX and RX phase compensation FIFOs are always enabled. Depending on the targeted data rate, you may bypass the byte serializer and deserializer blocks.
Figure 209. Standard PCS Low Latency 8-Bit PMA-PCS Interface WidthShows the available options for the standard PCS low latency 8-bit PMA-PCS interface width. The blocks shown as “Disabled” are not used but incur latency. The blocks shown as “Bypassed” are not used and do not incur any latency. The maximum frequencies are for the fastest devices.
Figure 210. Standard PCS Low Latency 10-Bit PMA-PCS Interface WidthShows the available options for the standard PCS low latency 10-bit PMA-PCS interface width. The blocks shown as “Disabled” are not used but incur latency. The blocks shown as “Bypassed” are not used and do not incur any latency. The maximum frequencies are for the fastest devices.
Figure 211. Standard PCS Low Latency 16-Bit PMA-PCS Interface WidthShows the available options for the standard PCS low latency 16-bit PMA-PCS interface width. The blocks shown as “Disabled” are not used but incur latency. The blocks shown as “Bypassed” are not used and do not incur any latency. The maximum frequencies are for the fastest devices.
Figure 212. Standard PCS Low Latency 20-Bit PMA-PCS Interface WidthShows the available options for the standard PCS low latency 20-bit PMA-PCS interface width. The blocks shown as “Disabled” are not used but incur latency. The blocks shown as “Bypassed” are not used and do not incur any latency. The maximum frequencies are for the fastest devices.