October 2007

Lattice Listens

Question:

How do I generate a LatticeSC PCS module to implement SFI-5 (SERDES Framer Interface Level 5)?    

Answer:

SFI-5 uses 17 SERDES channels running at 2.5Gbps. Lattice recommends creating two 8-bit SERDES-only flexiPCS modules for LatticeSC in IPexpress. One module should be created with all four channels and the other module should be created with just channel 0. Use the 4-channel flexiPCS four times and the 1-channel flexiPCS once to create the 17 channels. All of the channels must be transmit aligned. This transmit alignment is performed using two options of the flexiPCS. The first is to use the internal refclk. The internal refclk uses a balanced route to all flexiPCS quads resulting in minimal transmit skew across all quads.

The second is to sync, inside a quad, all of the serializers to minimize channel-to-channel skew. This is enabled when the Rx multichannel x4 alignment is used. SFI-5 uses an alignment scheme which the MCA does not support. So, enabling the Rx MCA to x4 alignment is only done to force transmit alignment. The MCA channel enables should not be enabled since the MCA will not support SFI-5 alignment. The MCA must be controlled via the autoconfig file since it is not an option in the 8-bit SERDES-only mode GUI. The line to add to the .txt file is: quad 19 40.