Embedded Computing problem

Design a 4-bit register with 2 control inputs s1 and s0, 4 data inputs I3, I2, I1 and I0, and 4 data outputs Q3, Q2, Q1 and Q0. When s1s0=00, the register maintains its value. When s1s0=01, the register loads I3..I0. When s1s0=10, the register clears itself to 0000. When s1s0=11, the register complements itself, so for example 0000 would become 1111, and 1010 would become 0101. (Refer to slide 17 of unit 4 power points to see an example)

slide 17 of unit 4 power points

Multifunction Registers Many registers have multiple functions Functions: Load, shift, clear (load all 0s) S1 so operation And retain present value, of course 0 0 Maintain present value o 1 Parallel load Easily designed using muxes 1 0 Shift right Just connect each mux input to achieve 1 1 (unused let's load 0s) desired function shr in 13 12 I1 IO s1 321.0 3.2.1.0 3 2 1 0 3 2 1 0 shr in 13 12 I1 Io s0 s1 SO Q3 Q2 Q1 Q0 (b) Q3 Q1 Q0 Q2 (a) Digital Design 2e 17 Copyright 2010 Frank Vahid