can a register have z as its value?

[tariq786]

i am simulating an opencores.com design and i see for certain clock cycles, some registers or flipflops have high impedance or z value.

I am wondering is it normal for registers or flip-flops to have z value?

Under what circumstance can a register or flip-flop get z value?

Note that the clock is working fine.

 

[iwpia50s]

I suppose one could design anything, but it practice, a register is almost never a "Z". Even in power switching designs you would use retention.