1. A method for performing a sleep operation in a system that includes a device under test and an emulator device, said method comprising: a) executing instructions on said device under test; b) emulating the functions of said device under test by operating said emulator device in lock-step fashion with said device under test; c) performing a sleep operation, comprising: c1) upon receiving a first signal from an operating program that indicates that a sleep function is to be performed, initiating said sleep function at said device under test; c2) in response to said initiating said sleep function, turning off one or more clock of said device under test; and c3) discontinuing execution of instructions that are performed in lock-step by said emulator device upon turning off said clock; d) when said sleep function has been completed by said device under test, turning on said clock and sending a second signal from said device under test to said emulator device; e) receiving said second signal at said emulator device; f) determining the number of clock signals received at said emulator device since said second signal was received; and g) resuming execution of said instructions that are performed in lock-step at said emulator device when said determined number of clock signals received at said emulator device since said second signal was received equals a predetermined value.