Overview

Product details

The XL4021B is an 8-stage parallel or serial input/serial output chip with common CLOCK and parallel/SERIALCONTROL inputs, a single serial data input, and separate parallel "JAM" inputs for each register stage. Each register stage is a D-type master-slave flip-flop. In addition to the output of stage 8, a "Q" output is also available from stages 6 and 7. In the XL4021B, the serial term is synchronous with the clock, while the parallel term is asynchronous. In both types, the inputs are controlled by the PARALLEL/SERIAL CONTROL inputs. When the PARALLEL/SERIAL control input is low, data is serially transferred into the 8-stage register synchronously with the positive transition of the clock line. When the parallel/serial control input is high, data is jammed into the 8-stage register via the parallel input lines, synchronously with the positive transition of the clock line. In the XL4021B, the CLOCK input of the internal stage is "forced" when asynchronous parallel input is made. This allows the use of multiple packages of extended registers.