Hold time can be negative, which means the data can change slightly before the clock edge and still be properly captured. violations can be serious in ASICs nAlso, this will be on the midterm Quiz EE183 Lecture 5 - Slide 16 Setup and Hold Times nSetup Time: the amount of time the synchronous input (D) must be stable before the active edge of the clock nHold Time: the amount of time the synchronous input (D) must be stable after the active edge of the clock STA checks this setup and hold violations. Hold Time Violation • Data not held long enough after latch edge – new data is too fast compared to the clock speed • Fix hold time violations – adding buffers to the data path – reduce buffer size in the data path – add more capacitance to the buffer output – time borrowing from setup time margin 26 Setup and Hold time. As long as the magnitude of these violations are small (like 100ps or so), then you can ignore them - the tools will fix this in route_design. If a chip is done with hold violations, we have “JUST DUMP” the chip.

Setup and hold violations.

In the above figure, the shaded …

Assume wire and 5. registers have no delay a) The setup time for the registers is 5 ns, and hold time is 8 ns. However, any decent set of layout tools can be set up to automatically fix these for you. This article assumes that the reader has at least a basic understanding of what a Flip-Flop is and how propagation delay affects designs. Since hold times are only fixed by route_design, it is normal to see some small hold time violations in a synthesized or placed (but not routed) design. View Forum Posts ... Setup/Hold time violation -- Frequency dependancy Originally Posted by BISH. Hold violations can't be helped, so fix the holds. It would of great help if you explain with a setup and hold violation example, where by changing frequency we can avoid setup violations , whereas the same is not possible with hold violation elimanation. Hold fixing seeks to avoid introducing both setup and DRC violations. What is meant by setup and/or hold violations: The ultimate aim of timing analysis is to get the design work at required frequency and with reliability.

Setup time and Hold time are important concepts to understand for every digital designer. If the Hold Time Violation is associated with a PERIOD constraint, the data path is faster than the clock skew. If a hold-critical register gets packed in the same ALM as its driving LUT, the router will add wire in front of the LUT to avoid hold time violations. While the hold time violation can be solved by inserting delay between the launching and capturing FF, nevertheless, one shall be careful that this does not create a new critical path. If a chip is done with some setup violations it can work by reducing the frequency. Hopefully the answers to these questions help determine the cause of the setup or hold time violation. Hold violations can't be helped, so fix the holds. If the data input is not constant the output of … If the data input is not constant the output of sequential element (FF) goes unpredictable state.

To avoid hold time violations: By adding delays (using buffers). Redesign the flip-flops to get lesser setup time. For D2 to be able to send its signal to Q2, it must be left unchanged for thold time after a clock edge.

Fig: Following figure shows that how data should propagate without hold violation . Fig: Following figure shows the condition of … To avoid setup time violations: The combinational logic between the flip-flops should be optimized to get minimum delay. violations can be serious in ASICs nAlso, this will be on the midterm Quiz EE183 Lecture 5 - Slide 16 Setup and Hold Times nSetup Time: the amount of time the synchronous input (D) must be stable before the active edge of the clock nHold Time: the amount of time the synchronous input (D) must be stable after the active edge of the clock
The resolution is similar to a Hold Time Violation in an OFFSET IN constraint, but decrease the clock skew instead of just the clock path delay. SETUP TIME & HOLD TIME EQUATIONS This section derives the equation for valid input window for a flip-flop to avoid set up and hold time violations. If there is setup and hold time violations in the design does not meet the timing requirements and the functionality of the design is not reliable. To avoid setup time violations: The combinational logic between the flip-flops should be optimized to get minimum delay.

6th May 2009, 09:51 #5. jjean. The setup time is the interval before the clock where the data must be held stable.
That is, during this time, a signal from D1 should not be able to race through the combinational logic Comb1 and make it to D2.