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WHY RESET IS USED..?
Reset is used to initialize the hardware design of
a system and to make system to known state from
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TYPES OF RESETS….
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Reset is of two types :-
1. Synchronous reset :-- a synchronous reset will reset
the circuit at active edge of clock .
Gives a completely synchronous circuit
Provides filtering for the reset signal, So circuit will
not be affected by glitches.
Will meet reset recovery time, as the deassertion will
happen within 1 clock cycle
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Reset needs to be stretched, if it is not long
enough to be seen at the active clock edge.
Requires presence of clock to reset the circuit.
Asynchronous reset may be required if there are
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internal tri state buffers.
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It is slow.
Synthesis will not be able to easily differentiate reset
from other signals. So this has to be taken care while
doing synthesis. Otherwise it may lead to timing
If there are gated clocks for power saving, this type of
reset won’t be suitable.
2. Asynchronous reset :-- asynchronous reset will reset
the circuit asynchronously i.e no matter with the
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Reset gets the highest priority.
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It is fast.
Does not require presence of clock to reset the circuit.
Reset line is sensitive to glitches.
May have metastability issues
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