Register the Inputs and Outputs of Your Design - 2022.1 English

Vitis Model Composer User Guide (UG1483)

Document ID
Release Date
2022.1 English

Register the inputs and outputs of your design. As shown below, this can be done by placing one or more Delay blocks with a latency 1 or Register blocks after the Gateway In and before Gateway Out blocks. Selecting any of the Register block features adds hardware.

Figure 1. Register Inputs and Outputs

Double registering the I/Os may also be beneficial. This can be performed by instantiating two separate Register blocks, or by instantiating two Delay blocks, each having latency 1. This allows one of the registers to be packed into the IOB and the other to be placed next to the logic in the FPGA fabric. A Delay block with latency 2 does not give the same result because the block with a latency of 2 is implemented using an SRL32 and cannot be packed into an IOB.