Vizio has discrete codes, and in previous installations we have found that using the discrete codes within the URC database via RF only worked for the off command. The discrete ON command would only work via IR and not RF. I had to create two separate TV devices for the remote, one that communicated via RF (Off Command) and one that communicated via IR (On Command). That has been the only reliable way for us to operate a Vizio when the client wants to have the remote power on and off devices as needed. Hope what I explained makes since, and to answer the original question most big name TV manufacturers have discrete commands.

URC Off Device Number 601 (Discrete Functions 2009)