Adv and DisAdv of Gated Clocks

Advantges:

1. used to save power by masking the clock to the flops.
2. used in clock switching circuits.
3. Reduces routing burden and area to some extent.
4. Ex: Suppose there are 8 D flops(DffL) with common load signal, we can replace all those loadable flops with simple D (Dff) flops and a clock gating circuit. This will reduce routing effort for the load signals to all flops. The area we are saving here is 8*(DffL/Dff). Of course we are adding clock gate area extra.

Disadvantages:

1. There should not be any glitch on the gating signal, and the gating signal should transit only during the clock's inactive level.
2. For DFT, the gating signal will be forced to a value so that the clock will be active during DFT testing.
3. Introduces delay on the clock line.

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