A method for changing operation of a device, comprising: sending target device descriptors to the device's device emulator, which processes and stores the descriptors as the current descriptors in memory, and the device emulator responding to a query from a host simulating operation of the target device. Using the method, the host recognizes the device as a different, target device, such as printers, MFPs, peripherals, digital cameras, etc. Device emulation enables installation and other testing of a new and yet unavailable target device under development. The methods also include USB device enumeration, making a print job containing extended PJL commands and sending it using a generic device driver, emulator firmware analyzing and storing the descriptors in registers, sending a line reset command to simulate device detachment and reattachment, and meeting timing requirements of USB detached and attached states.