A processing system that interacts with external devices has a processor, a memory, and a controller. The memory stores templates that provide access protocol information about the external devices. When an external device is to be accessed, the operating system, which is stored in the memory, instructs the processor to perform the access to the external device. The processor puts the information about the external device on the address portion of the system bus where it is received and interpreted by the controller. The controller in turn retrieves the template for the external device as indicated by the information that was received. After retrieving the template, the controller outputs the information, in the manner indicated by the template, on an external interface bus where the external device is also coupled. The external device then responds according to the information that the controller put on the external interface bus.