PAM4 encodes 2-bits of binary data to into four voltage levels. Through this tutorial, we can create an example to verify designs with PAM4 signals.
Since four voltage levels are not supported by implementation tools. So the PAM4
connections are created as regular single bit wire. For simulation purposes, the PAM4
signals of the design are made accessible in testbench via integer ports of a special
module (xil_dut_bypass) that gets generated as part of
this flow. The generated bypass module is not part of the DUT but has direct access to
PAM4 signals of the DUT. This module can be instantiated in testbench to directly
drive/observe PAM4 signals.