[SOLVED] need_to_reset_all_flipflops_in_a_design

[ashu211188]

In a design do all flops require reset? If reset is not present for some of the flops then wat will happen?
I know that the reset is used to bring the flipflops in known state. but is there any other reason.

Basically in a design why should we reset all the flops?

Can't a powerdown switch work?
- I guess it can give garbage value

 

[vipinlal]

A power down switch will reset all the flip flops to '0'. But it will also erase the code available in the volatile memory in fpga.

Also a reset is useful when different flipflops need to be reset into different states(either '0' or '1').

 

[ashu211188]

thanks Vipinlal.

If in a design, I have 10 flops and out of those 10 flops, 6 have reset pin but the other 4 doesnt have reset facility, will it do?
or we need to have the reset logic for all 10 flops?

 

[FvM]

A power down switch will reset all the flip flops to '0'.

The power on-reset is often not sufficient to achieve a known state, because it's not released synchronously to the system clock.

If in a design, I have 10 flops and out of those 10 flops, 6 have reset pin but the other 4 doesnt have reset facility, will it do?
or we need to have the reset logic for all 10 flops?

The question can be only answered by analyzing the system in detail. If the system state advances to the required state despite arbitrary initial states of the 4 FFs, you don't necessarily need to reset them. Obviously resetting all FFs in a system (and release the reset synchronously to the clock) is the best way to achieve a known state.