344 - For SERDES/PCS-based Lattice devices, can I use the CTC FIFO in the hard PCS even if I connect the PCS to the SGMII/GbE PCS IP?
The answer depends both on device family and data rate:
- In the case of the LatticeSC device, the user can only use the CTC in the SGMII/GbE PCS IP.
- In the case of the LatticeECP2M and LatticeECP3 devices, the use of the hard PCS CTC depends on the mode of operation:
- You cannot use the PCS CTC when operating at 10 or 100 Mbps (in SGMII mode). The PCS CTC is not deep enough to handle IDLE addition/deletion at these two rates because data is repeated 10 times (100 Mbps) or 100 times (10 Mbps). Instead, you need to use the deeper CTC in the SGMII/GBE PCS.
- You can use the CTC in the PCS if the SGMII/GBE PCS IP will run at 1000Mbps. This applies to GbE mode or SGMII modes at 1000 Mbps operation. When you use the CTC in the hard PCS, the following requirement needs to be met: you need to make sure the xmit_ch# input pin on the PCS is asserted during Auto Negotiation. For more information on this requirement, please refer to the LatticeECP3 PCS user guide (TN1176). Also note that, by default, the hard PCS autoconfiguration file in the SGMII/GbE PCS IP reference design that IPexpress generates does disable the hard PCS CTC. You will need to manually edit the file to enable the CTC.