An area of high speed temporary memory used to interface parallel and serial circuits. A PISO (parallel-in, serial-out) shift register has parallel input ports and serial output ports. A SIPO (serialin, parallel-out) shift register has serial input ports and parallel output ports. See also parallel communications, register, serial communications, and shift register.
A high-speed circuit that holds some number of bits for the purpose of shifting them left or right. It is used internally within the processor for multiplication and division, serial/parallel conversion and various timing considerations. See register.