Contents
- 1 What are the requisites for the synthesis tools to implement clock gating?
- 2 How do I stop my clock gating?
- 3 Why do we need clock gating?
- 4 What is clock gating cell?
- 5 How do I fix clock gating setup violations?
- 6 What are clock gating cells?
- 7 What is use of latch in clock gating cell?
- 8 What is a lock up latch?
- 9 Why is clock gating important in clock design?
- 10 How are timing constraints used in RTL design?
What are the requisites for the synthesis tools to implement clock gating?
All the traditional synthesis tools implement clock gating based on register bit-width. Power synthesis implements a clock gate if the register bit-width is equal to or more than the one specified by the user.
How do I stop my clock gating?
Clock Gating Overview These glitches can be removed by introducing a negative edge triggered FF (assuming downstream FFs are positive edge) or low-level sensitive latch at the output of the clock enable signal. This will make sure that any glitch in the clock enable signal will not be visible to the gated clock output.
What is clock gating in VLSI?
if latch has single clock gate in fanout then icg (integrated clock gate – has or, latch,and cells integrated) cell gets used. for ICG, 2 inputs go to OR cell (test and enable signals). OR output goes to latch d pin and latch output goes to AND cell. Both latch and clock gate get same clock input.
Why do we need clock gating?
Clock gating is a popular technique used in many synchronous circuits for reducing dynamic power dissipation, by removing the clock signal when the circuit is not in use. Clock gating saves power by pruning the clock tree, at the cost of adding more logic to a circuit.
What is clock gating cell?
A clock gating check occurs when a gating signal can control the path of a clock signal at a logic cell. Logic cell where clock gating occurs is also referred to as gating cell. One condition for a clock gating check is that clock that goes through cell must be used as a clock downstream.
Why do we use clock gating?
How do I fix clock gating setup violations?
How to mitigate this problem: To prevent violations, its best to sync the enable signal with respect to the clock it is gating. This is achieved by using a latch which is transparent only during the inactive phase of the clock.
What are clock gating cells?
What is clock gating cells?
A clock gate is a standard design cell that receives the clock and a gating signal as an input and ensures that the clock propagates only when it’s required depending upon the gating signal.
What is use of latch in clock gating cell?
2.1 Types. In latch based clock gating, latch is used as control element, it controls the Enable pin. In negative clock cycle, latch is al- lowed to reflect the change of Enable pin. In positive clock cycle, output of latch remains fixed. The high output of latch allows the clock to reach sequential logic.
What is a lock up latch?
A lock-up latch is a transparent latch used to avoid large clock skew and mitigate the problem in closing hold timing due to large uncommon clock path. From timing perspective lock-up latches can be the best solution to avoid large uncommon path between the clocks of two flops.
When to use the clock gating signal in RTL?
The clock gating signal should only toggle when the latch is closed, otherwise there is a chance for glitches and metastability issues. For an active high latch, the gating signal should toggle on the falling edge of the clock. Rising edge for active low latches.
Why is clock gating important in clock design?
Hence, reducing clock power is very important. Clock gating is a key power reduction technique used by many designers and is typically implemented by gate-level power synthesis tools.
How are timing constraints used in RTL design?
Timing Constraints (optional) – There are several Synopsys Design Constraints (SDC) timing constraints which may be useful for power estimation, such as set_case_analysis or set_output_load. An SDC file may be optionally supplied. 3 HOW GOOD ARE EXISTING ENABLES IN THE RTL DESIGN?
How is Spyglass power used in clock gating?
SpyGlass-Power can calculate the effect of enables on power savings instead of just register width as shown in Figure 12. It can also generate a “don’t touch” script for negative power opportunities, which the designer can use with the synthesis tool and discard the registers that dissipate more power with clock gating.