Redo problem C13-2, adding recirculation and Left/Right (lr) control to the shifting sequence. When = ‘0', shift left; when ‘1', shift right. The simulation and FPGA demonstration should show recirculating data bits with left/right direction control.
Problem C13-2
The VHDL program in Figure 13-9(a) is the implementation of a parallel-load, shift-right shift register.
(a) Download the files shift_b.vhd and shift_b.vwf. Save these files with the new name prob_c13_2.vhd and prob_c13_2.vwf.
(b) Create a new project and compile and simulate this program. (Remember, the Entity name must be changed to the new name in all three locations before attempting to compile.)
(c) Convert the program to a recirculating shift register. (The data leaving q0 is recirculated back to q3.)
(d) Run the simulation demonstrating the shifting sequence q3-to-q2-toq1-to-q0-to-q3, etc.
(e) Download your design of part (c) to an FPGA IC. Discuss your observations of the q output LEDs with your instructor as you demonstrate the recirculating shift-right operation. Use a debounced switch for n_cp. (The DE-2 has debounced pushbuttons.)