Commands are passed between first and second asynchronous clock domains. Unique coded command signals are inserted into a data stream transmitted from the first asynchronous clock domain to the second asynchronous clock domain. They are passed without change from the first asynchronous clock domain to the second asynchronous clock domain through an elastic buffer. The unique coded command signals are then decoded in receiver circuitry in the second asynchronous clock domain. Process circuitry in the second asynchronous clock domain is controlled according to the decoded command signals.