Apparatus and method for adjusting the skew of a timing signal using propagation delay time of signals generated by a ring oscillator forming a digital circuit

• US 5,745,533 A
• Filed: 05/30/1995
• Issued: 04/28/1998
• Est. Priority Date: 06/02/1994
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Asada, Yoshimi, Nakada, Tatsumi
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): LUTHER, WILLIAM A
• Application Number:
  US08/452,539
• Time in Patent Office: 1,064 Days
• Field of Search: 375/354, 375/371, 375/377, 375/376, 371/1, 327/141, 327/161, 327/156, 327/144, 395/551, 395/553, 395/559, 395/558, 395/556, 326/93, 326/96, 340/825.05, 340/825.14, 340/825.2, 340/825.57, 340/825.61
• US Class Current: 375/354
• CPC Class Codes: G06F 1/10 Distribution of clock signals , e.g. skew
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging

Abstract

When a selector selects a first input terminal, a first loop circuit is formed including first and second input buffer circuits and an output buffer circuit. When the selector selects a second input terminal, a second loop circuit is formed including the first input buffer circuit and the output buffer circuit. When the selector selects a third input terminal, a third loop circuit is formed including the first input buffer circuit, a variable delay line (VDL), and the output buffer circuit. From the oscillating frequencies of loop circuits each formed as a ring oscillator, their respective signal delay times are obtained. By equalizing characteristics of first and second input buffer circuits, through a mutual operation using the signal delay times of respective loop circuits, a propagation delay time over a timing signal supply path including the first input buffer circuit and the VDL and stretching to a flip-flop is obtained precisely.

Claims

1. A skew adjustment apparatus for use in a digital system having a timing signal supply path for supplying a timing signal to a digital circuit, comprising:

first delay means provided on the timing signal supply path;

propagation delay time adjustment means provided on the timing signal supply path for adjusting a propagation delay time of the timing signal supply path;

second delay means connected to an output terminal of said propagation delay time adjustment means and an input terminal of said first delay means; and

selection means for selectively forming a first loop circuit operating as a ring oscillator, the first loop circuit including said first delay means said second delay means and said propagation delay time adjustment means the first loop circuit having a first propagation delay time, or a second loop circuit operating as a ring oscillator, the second loop circuit including said first delay means and said second delay means, the second loop circuit having a second propagation delay time.

2. The skew adjustment apparatus according to claim 1, wherein:

said propagation delay time adjustment means adjusts the propagation delay time of the timing signal based on a result obtained by subtracting the second propagation delay time from the first propagation delay time.

3. The skew adjustment apparatus according to claim 1, further comprising:

third delay means connected to the timing signal supply path, said third delay means having a propagation delay time equivalent to the propagation delay time of said first delay means, wherein;

said selection means selectively forms one of the first loop circuit, the second loop circuit, and a third loop circuit including said first delay means, said second delay means and said third delay the third loop circuit having a third propagation delay time.

4. The skew adjustment apparatus according to claim 3, wherein:

said propagation delay time adjustment means adjusts the propagation delay time of the timing signal supply path based on a difference obtained by subtracting a propagation delay time of said second delay means from the first propagation delay time, through an operation using the first propagation delay time, the second propagation delay time, and the third propagation delay time.

5. A skew adjustment apparatus for use in a digital system having a plurality of timing signal supply paths for supplying a timing signal to display circuits, the skew adjustment apparatus comprising:

a plurality of first delay means wherein a first delay means is provided on each of said plurality of timing signal supply paths;

a plurality of propagation delay time adjustment means, wherein a propagation delay time adjustment means is provided on each of said plurality of timing signal supply paths for adjusting a propagation delay time for each corresponding timing signal supply path;

a plurality of second delay means, wherein a second delay means is connected between each output terminal of a corresponding said propagation delay time adjustment means and an input terminal of a corresponding said first delay means; and

a plurality of selection means, wherein a selection means is provided for each timing signal path for selectively forming a first loop circuit including said first and second delay means and said propagation delay time adjustment means or a second loop circuit including said first and second delay means.

6. A skew adjustment apparatus according to claim 5, further comprising, a plurality of third delay means each having a propagation delay time equivalent to that of said first delay means wherein each third delay means being connected to corresponding one of said plurality of timing signal supply paths, wherein:

each of said selection means selectively forms one of the first loop circuit, the second loop circuit, and a third loop circuit including said first, second and third delay means.

7. A skew adjustment apparatus for use in a digital system having a timing signal generation circuit for generating a timing signal generation circuit for generating a timing signal and a timing signal supply path for transferring the timing signal, comprising:

propagation delay time adjustment means provided on said timing signal supply path for adjusting a propagation time of the timing signal supply path;

first delay means provided on said timing signal supply path;

a first return path connected to said timing signal supply path;

second delay means provided on said first return path;

a second return path connected to said first return path;

third delay means, having a propagation delay time equivalent to a propagation delay time of said second delay means, provided on said second return path; and

selection means for selectively forming a first loop circuit including said first and second delay means and said propagation delay time adjustment means or a second loop circuit including said first, second, third delay means and said propagation delay time adjustment means.

8. The skew adjustment apparatus according to claim 7, wherein:

said propagation delay time adjustment means adjusts a propagation delay time of said timing signal supply path based on a difference obtained by subtracting a propagation delay time of said second delay means from a propagation delay time of the first loop circuit, through an operation using a propagation delay time of the first loop circuit and a propagation delay time of the second loop circuit.

9. The skew adjustment apparatus according to claim 8, wherein:

said selection means selectively forms one of the first loop circuit, the second loop circuit and a third loop circuit including said first and second delay means.

10. The skew adjustment apparatus according to claim 9, wherein:

said propagation delay time adjustment means adjusts the propagation delay time over said timing signal supply path by subtracting a propagation delay time of said second delay means from a propagation delay time of the first loop circuit, through an operation using the propagation delay time of the first loop circuit, the propagation delay time of the second loop circuit, and a propagation delay time of the third loop circuit.

11. A skew adjustment apparatus for use in a digital system having a timing signal generation circuit for generating a timing signal and a plurality of timing signal supply paths for transferring the timing signal, comprising:

a plurality of propagation delay time adjustment means, wherein a propagation delay time is provided on each of said plurality of timing signal supply paths;

a plurality of first delay means, wherein a first delay means is provided on each of said plurality of timing signal supply paths;

a plurality of first return path, wherein a first return path is connected to each of said plurality of timing signal supply paths;

a plurality of second delay means, wherein a second delay means is provided on each of said first return path;

a plurality of second return path, wherein a second return path is connected to each of said first return path;

a plurality of third delay means, each having a propagation delay time equivalent to that of a corresponding said second delay means, wherein a third delay means is provided on each of said second return path; and

a plurality of selection means provided for each timing signal supply paths, each selection means selectively forming a first loop circuit including corresponding ones of said first and second delay means and said propagation delay time adjustment means or a second loop circuit including corresponding ones of said first, second and third delay means and said propagation delay time adjustment means.

12. The skew adjustment apparatus according to claim 11, wherein:

each of said selection means selectively forms one of said first loop circuit, said second loop circuit, and a third loop circuit including corresponding ones of said first and second delay means.

13. A skew adjustment apparatus for use in a digital system having a timing signal supply path for supplying a timing signal to a digital circuit, comprising:

a variable delay line provided on the timing signal supply path;

a first input buffer circuit provided on the timing signal supply path;

a first return path connected to the timing signal supply path;

an output buffer circuit provided on said first return path;

a second return path connected to the timing signal supply path;

a second input buffer circuit, having a propagation delay time equivalent to a propagation delay time of said first input buffer circuit, provided on said second return path; and

a selector for selectively forming one of a first loop circuit including said first input buffer circuit, said variable delay line and said output buffer circuit, a second loop circuit including said first input buffer circuit and said output buffer circuit, and a third loop circuit including said first and second input buffer circuits and said output buffer circuit.

14. A skew adjustment apparatus for use in a digital system having a timing signal generation circuit for generating a timing signal and a timing signal supply path for transferring said timing signal, comprising:

a variable delay line provided on the timing signal supply path;

an output buffer circuit provided on the timing signal supply path;

a first return path connected to the timing signal supply path;

a first input buffer circuit provided on said first return path;

a second return path connected to said first return path;

a second input buffer circuit, having a propagation delay time equivalent to a propagation delay time of said first input buffer circuits provided on said second return path; and

a selector for selectively forming a first loop circuit including said output buffer circuit, said first input buffer circuit and said variable delay line or a second loop circuit including said output buffer circuit, said first and second input buffer circuits and said delay line.

15. A skew adjustment apparatus for use in a digital system having a plurality of timing signal supply paths for supplying a plurality of timing signals to digital circuits, comprising:

a variable delay line provided for each of the plurality of timing signal supply paths;

a first input buffer circuit provided on each of the plurality of timing signal supply paths;

a first return path connected to each of the plurality of timing signal supply paths;

an output buffer circuit provided on said first return path;

a second return path connected to each of the plurality of timing signal supply paths;

a second input buffer circuit, having a propagation delay time equivalent to a propagation delay time of said first input buffer circuit, provided on said second return path; and

a selector for selectively forming one of a first loop circuit including said first input buffer circuit and said variable delay line and said output buffer circuit, a second loop circuit including said first input buffer circuit and said output buffer circuit, and a third loop circuit including said first and second input buffer circuits and said output buffer circuit.

16. A skew adjustment apparatus for use in a digital system having a plurality timing signal supply path for supplying a timing signal to a plurality of digital circuit, comprising:

a variable delay line provided for each of the plurality of timing signal supply paths;

an input buffer circuit provided for each of the plurality of timing signal supply paths;

a first return path connected to said plurality of timing signal supply paths;

an output buffer circuit provided on said first return path;

a second return path connected to each of said plurality of timing signal supply paths; and

a selector for selectively forming a first loop circuit including said input buffer circuit, said variable delay line and said an output buffer circuit or a second loop circuit including said output buffer circuit.

17. A propagation delay time measurement apparatus for use in a digital system having a timing signal supply path for supplying a timing signal to a digital circuit comprising:

first delay means provided on the timing signal supply path;

propagation delay time adjustment means provided on the timing signal supply path;

second delay means, connected between an output terminal of said propagation delay time adjustment means and an input terminal of said first delay means; and

selection means for selectively forming a first loop circuit including said first and said second delay means and said propagation delay time adjustment means or a second loop circuit including said first and said second delay means, and wherein;

a propagation delay time of a part of said timing signal supply path is detected by subtracting a propagation delay time of the second loop circuit from a propagation delay time of the first loop circuit.

18. The propagation delay time measurement apparatus according to claim 17, further comprising third delay means, having a propagation delay time equivalent to a propagation delay time of said first delay means, connected to said timing signal supply path, wherein:

said selection means selectively forms one of said first loop circuit, said second loop circuit, and a third loop circuit including said first, second and third delay means; and

wherein;

a propagation delay time of said second delay means is subtracted from a propagation delay time of said first loop circuit through an operation using a propagation delay time of the first loop circuit, a propagation delay time of the second loop circuit, and a propagation delay time of the third loop circuit.

19. A propagation delay time measurement apparatus for use in a digital system having a timing signal generation circuit for generating a timing signal and a timing signal supply path for transferring said timing signal, comprising:

propagation delay time adjustment means provided on the timing signal supply path;

first delay means provided on the timing signal supply pat;

second delay means provided on said first return path;

a second return path connected to said first return path;

third delay means, having a propagation delay time equivalent to a propagation delay of said second delay means, provided on said second return path; and

selection means for selectively forming a first loop circuit including said first and second delay means and said propagation delay time adjustment means or a second loop circuit including said first, second, and third delay means and said propagation delay time adjustment means, and wherein;

a propagation delay time of a part of said timing signal supply path is obtained, by subtracting a propagation delay time of said second delay means from a propagation delay time of the first loop circuit, through an operation using a propagation delay time of the first loop circuit and a propagation delay time of the second loop circuit.

20. The propagation delay time measurement apparatus according to claim 19, wherein:

said selection means selectively form one of said first loop circuit, said second loop circuit, and a third loop circuit including said first and second delay means; and

wherein;

a propagation delay time of said second delay means is subtracted from a propagation delay time of the first loop circuit, through an operation using a propagation delay time of the first loop circuit, a propagation delay time of the second loop circuit, and a propagation delay time of the third loop circuit.

21. A skew adjustment method for adjusting a signal delay time over a timing signal supply path which supplies a timing signal to a digital circuit, the method comprising the steps of:

forming a first loop circuit including a first delay circuit and a variable delay line on the timing signal supply path, and a second delay circuit not on the timing signal supply path;

obtaining a propagation delay time of the first loop circuit by emitting a first pulse that said first loop circuit oscillates;

forming a second loop circuit including the first and second delay circuits;

obtaining a propagation delay time of the second loop circuit by emitting a second pulse that said second loop circuit oscillates; and

adjusting a signal delay time over the timing signal supply path, by changing a propagation delay time of the variable delay line, based on the propagation delay time of the first loop circuit and the propagation delay time of the second loop circuit.

22. The skew adjustment method according to claim 21, further comprising the steps of:

forming a third loop circuit including a third delay circuit, having a propagation delay time equivalent to a propagation delay time of the first delay circuit, and the first and second delay circuits, the third delay circuit not being on said timing signal supply path;

obtaining a propagation delay time of the third loop circuit by emitting a third pulse that said third loop circuit oscillates; and

adjusting the signal delay time over the timing signal supply path by changing a propagation delay time of the variable delay line, based on the propagation delay time of the first loop circuit, the propagation delay time of the second loop circuit, and the propagation delay time of the third loop circuit.

23. A skew adjustment method for adjusting a signal delay time over a timing signal supply path which supplies a timing signal to a digital circuit, the method comprising the steps of:

forming a first loop circuit including a first delay circuit, a variable delay line on the timing signal supply path and a second delay circuit not on said timing signal supply path;

obtaining a propagation delay time of the first loop circuit by emitting a first pulse that the first loop circuit oscillates;

forming a second loop circuit including the first and second delay circuits, the variable delay line and a third delay circuit, having a propagation delay time equivalent to a propagation time of the first delay circuit, not provided on the timing signal supply path;

obtaining a propagation delay time of said second loop circuit by emitting a second pulse that the second loop circuit oscillates; and

adjusting a signal delay time of the timing signal supply path by changing a propagation delay time of the variable delay line, based on the propagation delay time of the first loop circuit and the propagation delay time of the second loop circuit.

24. A skew adjustment method for adjusting a signal delay time of a timing signal supply path which supplies a timing signal to a digital circuit, the method comprising the steps of:

forming a first loop circuit from the timing signal supply path and a return path;

obtaining a propagation delay time of the first loop circuit by emitting a first pulse that the first loop circuit oscillates;

forming a second loop circuit using the return path;

obtaining a propagation delay time of the second loop circuit by emitting a second pulse that the second loop circuit oscillates;

obtaining a signal delay time of the timing signal supply path using the propagation delay time of the first loop circuit and the propagation delay time of the second loop circuit; and

adjusting the signal delay time of the timing signal supply path, based on the obtained signal delay time of the timing signal supply path.

25. The skew adjustment method according to claim 24, further comprising the steps of:

forming a third loop circuit using the return path;

obtaining a propagation delay time of the third loop circuit by emitting a third pulse that the third loop circuit oscillates;

obtaining the signal delay time of the timing signal supply path using the propagation delay time of the first loop circuit, the propagation delay time of the second loop circuit, and the propagation delay time of the third loop circuit; and

adjusting the signal delay time of the timing signal supply path, based on the obtained signal delay time over the timing signal supply path.