I/O-Port for Digital Processors, addressable as a register
Original Publication Date: 2000-Jan-01
Included in the Prior Art Database: 2003-Jul-22
Conventional ports for external data input and output on a digital processor are accessible through a memory-mapped interface so that the I/O-port is addressed in the same way as memory. Such addressing is in most cases realized as indirect addressing, leading to the overhead of loading the I/O-port address into the base register first. One solution to avoid this overhead is to implement the addressing of the I/O-port as a register access. The timing of transfers between port and processor is the same as of usual register accesses, and the data transfer itself is bitwise addressable. An additional op-code for the port can be sent together with other data transfer information in one command, making it suitable especially for operations such as high-speed modem communications and bit manipulation.