synchronus reset with simple respected clock.it is required more no of gates,and it is didnt have metastabilty problem.it is working is slow. : f* S; T# Z2 a0 Y" i. V4 v 6 i) J# s7 i+ e- ?: K# p* xasynchronous reset with out respected to the clock.it is required less no .of gates.it is suffer to the metastability problem.it is working is fast