An implantable medical device with internal processor is configured for diagnostic emulation with an external processor to enhance diagnostic testing with capabilities such as faster testing and more realistic testing. The implantable medical device can be a wide variety of implantable devices such as neuro stimulators, pacemakers, defibrillators, drug delivery pumps, diagnostic recorders, cochlear implants, and the like. The external processor is coupleable to the medical device to execute software involving medical device components with a bus switch coupled to the address bus, the data bus, and the internal processor. The bus switch has a bus switch external connector that when activated is configured to couple an external processor through the address bus external connection to the address bus and the external processor through the data bus external connector to the data bus. When the external processor is coupled to the medical device, the internal processor is decoupled from the address bus and data bus.