Automatic delay adjustment for static timing analysis

• US 5,210,700 A
• Filed: 02/20/1990
• Issued: 05/11/1993
• Est. Priority Date: 02/20/1990
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Tom, David
• Primary Examiner(s): Trans, Vincent N.
• Application Number:
  US07/482,234
• Time in Patent Office: 1,176 Days
• Field of Search: 364/488, 364/489, 364/490, 364/578
• US Class Current: 716/108
• CPC Class Codes: G06F 30/3312 Timing analysis

Abstract

Delay analysis in logic simulation is enhanced by providing, in a simulation model of a logic circuit, a timing delay tag on each circuit path connecting the output of a first with the input of the second circuit element. Each circuit leg is given a delay value and a clock phase tag providing information about how the delay value is clocked. The clock phase tags correspond to respective phases of a multi-phase circuit clock and relate the delay values to particular clock phases. The phase tag also indicates whether the signal on the data path is triggered by the rising or falling edge of the specified clock phase. At circuit nodes, clock phase tags are concatenated. Thus, if a clocked circuit element responds to an input signal which is a composite of several upstream output signals, the concatenated clock phase tags and delay values can be analyzed to determine if a timing adjustment is required. The information further supports the automatic adjustment of delay value, if needed.

Claims

1. In a programmed computer apparatus for analyzing timing delays in a multi-phase-clock logic network under static conditions, an improvement for analyzing signal delay through the logic network, the improvement comprising:

simulating means for providing a logical counterpart of the logic network which represents a multi-phase clock, elements of the logic network and connections between those elements, the elements including clocked elements which respond to the multi-phase clock by storing data signals;

a data object representing a data signal propagating in the logic network, the data object including a first data field representing a phase of the multi-phase clock during which a data signal is clocked by the logic network and a second data field representing a time by which the data signal is delayed by propagation in the logic circuit;

propagating means for applying the data object to a representation of a clocked element in the logic network, the clocked element being triggered by a particular phase of the multi-phase clock; and

delay means connected to the propagating means for comparing the phase represented by the first data field with a representation of the particular phase to change the second field to a path delay value representing the cumulative delay of the data signal through the clocked element.

2. The improvement of claim 1 further including, in the delay means, an adjustment means for comparing the phase represented by the first data field with the representation of the particular phase to produce an adjustment value by which the second field is adjusted.

3. The improvement of claim 1 further including, in the data object, a clock edge representation corresponding to an edge of the particular phase of the multi-phase clock which triggers the clocked element.

4. A static timing analysis system, including a programmed computer apparatus for analyzing timing delays in a logic design, comprising:

means in the programmed computer apparatus for simulating a logic design by providing representations of a logic clock, logic elements, and connections between the logic elements, the logic elements including clocked elements triggered by the logic clock;

a signal representation in the programmed computer apparatus of a signal propagating in the logic design, the signal representation including a clock tag identifying a first phase of the logic clock during which the signal is clocked in the logic design;

propagating means in the programmed computer apparatus for applying the signal representation to a representation of a clocked element in the logic design, the clocked element being triggered by a second phase of the logic clock to move the signal to an output of the clocked element; and

delay means in the programmed computer apparatus connected to the propagating means and responsive to the clock tag for comparing the first phase and second phase to produce a representation of the cumulative delay of the signal representation through the clocked elements.

5. The static timing analysis system of claim 4 wherein the signal representation includes a path delay having a value representing a cumulative propagation delay of the signal up to the clocked element.

6. The static timing analysis system of claim 5 wherein the delay means produces the representation of cumulative delay by combining the cumulative propagation delay with a block delay representing a signal delay through the clocked element for the signal.

7. The static timing analysis system of claim 6 wherein the delay means is further for placing the representation of the cumulative delay in the path delay.

8. The static timing analysis system of claim 4 wherein the representation of the cumulative delay includes a first value representing a cumulative delay to propagate a logical high signal and a second value representing a cumulative delay to propagate a logical low signal.

9. The static timing analysis system of claim 4 further including, in the delay means, an adjustment means for comparing the first and second phases to produce an adjustment value for adjusting the cumulative delay to account for a clock cycle difference between the first and second phases.

10. A computer-implemented method for conducting static timing analysis of a logic design, the logic design including a multi-phase logic clock, circuit logic elements, and connections between the circuit logic elements, the circuit logic elements including clocked elements which are triggered by the multi-phase clock, the method including the steps of:

representing a first signal in the logic design with a first data object including a first field containing a clock value representing a clock phase during which the first signal is clocked in the logic design and a second field containing a time value representing a time by which the first signal is delayed in the logic design;

simulating the application of the first signal to an input pin of a clocked element which is triggered by a particular phase of the multi-phase clock;

determining a cumulative delay value representing the cumulative delay of the first signal at an output pin of the clocked element in response to the clock phase in the first field and the particular phase; and

changing the first field to a value representing the particular phase and changing the second field value to the cumulative delay value.

11. The method of claim 10, further including:

comparing the clock value with the particular phase to determine whether the clock phase apparently occurs later than the particular phase; and

if the clock phase apparently occurs later than the particular phase, adjusting the time value to a value occurring before the particular phase.

12. In a computer apparatus programmed for analyzing timing delays in a multi-phase-clock logic network under static conditions, an improvement for analyzing signal delay through the logic network, the improvement comprising:

simulating means for providing a logical counterpart of the logic network which represents a multi-phase clock, elements of the logic network and connections between those elements, the elements including clocked elements which respond to the multi-phase clock by storing data signals;

a first data object representing a data signal propagating from an element in the logic network, the first data object including a first data field representing a first phase of the multi-phase clock during which said data signal is clocked by the logic network and a second data field representing a first time by which the data signal is delayed in the logic network;

a second data object representing said data signal, the second data object including a first data field representing a second phase of the multi-phase check during which said data signal is clocked by the logic network and a second data field representing a second time by which the data signal is delayed in the logic network;

propagating means for applying the first and second data objects to a representation of a clocked element being triggered by a third phase of the multi-phase clock; and

delay means connected to the propagating means for comparing the first and second phases represented by the first fields in the first and second data objects, respectively, with a representation of the third phase to change the second field of the first or second data object to a path delay value representing the cumulative delay value of the data signal through the clocked element.

13. The improvement of claim 12, wherein the delay means includes an adjustment means for comparing the first phase with the third phase to produce an adjustment value by which the second field of the first data object is changed.

14. The improvement of claim 13 wherein the adjustment value is a multiple of a multi-phase clock cycle time.