barrettotte / barrel-shifter-16

16-bit barrel shifter

barrel-shifter-16

16-bit barrel shifter

A barrel shifter allows multiple bit shifts in a single clock cycle using only combinatorial logic.

Synthesized in Vivado and tested on Basys 3 Artix-7 (XC7A35TCPG236-1).

The top module sets up a 16-bit barrel shifter with an arbitrary start value. The start value can be shifted by one using the left and right buttons.

I made this to learn the basics of running VHDL on an FPGA. I also plan on using a barrel shifter in my homebrew CPU project so I needed to figure out how this circuit works.

Circuit

66 2x1MUX

Logisim Evolution circuit logisim/barrel_shifter.circ

References

• https://en.wikipedia.org/wiki/Barrel_shifter
• https://digilent.com/reference/programmable-logic/basys-3/start
  • https://digilent.com/reference/_media/reference/programmable-logic/basys-3/basys-3-sch-public-rev-d.pdf
• https://github.com/Digilent/digilent-xdc/blob/master/Basys-3-Master.xdc