Pattern trigger in a coherent timebase
A method and apparatus for acquiring a signal employing a coherent timebase are provided. The method comprises the steps of defining a pattern length count of a repetitive pattern in a signal to be acquired, defining a number of samples per unit interval, and providing data strobes synchronous to a coherent timebase. An arbitrary one of the data strobes is designated as a timing for a potential trigger. A number of subsequent data strobes is counted in accordance with the pattern length count times the samples per unit interval and a portion of the signal corresponding to the pattern length count times the samples per unit interval is acquired beginning at a point in the signal defined by the designated arbitrary data strobe. Thereafter one or more additional portions of the signal are acquired corresponding to the pattern length count times the samples per unit interval at a point in the signal defined by when the number of subsequent data strobes reaches the pattern length count times the samples per unit interval.
1. A method for acquiring a signal employing a coherent timebase, comprising the steps of:
defining a pattern length count of a repetitive pattern in a signal to be acquired;
defining a number of samples per unit interval;
providing data strobes synchronous to a coherent timebase;
designating an arbitrary one of the data strobes as a timing for a potential trigger;
counting a number of subsequent data strobes in accordance with the pattern length count times the samples per unit interval;
acquiring a portion of the signal corresponding to the pattern length count times the samples per unit interval, beginning at a point in the signal defined by the designated arbitrary data strobe; and
acquiring one or more additional portions of the signal corresponding to the pattern length count times the samples per unit interval at a point in the signal defined by when the number of subsequent data strobes reaches the pattern length count times the samples per unit interval.
2. The method of claim 1 , wherein a counter for storing the data strobe counting is reset to zero each time it reaches the pattern length count times the samples per unit interval.
3. The method of claim 2 , wherein each time the counter reaches the pattern length count, a potential trigger is defined.
4. The method of claim 3 , wherein a portion of the signal is acquired when a potential trigger is reached, and an additional designation to acquire a signal is present.
5. The method of claim 4 , wherein the additional designation is input by a user.
6. The method of claim 1 , wherein the additional portions of the signal are offset to the first portions in accordance with a delay set by a phase counter from the point in the signal defined by when the number of subsequent data strobes reaches the pattern length count times the samples per unit interval.
7. The method of claim 1 , wherein the portions of the signal acquired include digitized samples.
8. The method of claim 7 , wherein the digital samples acquired from the initial portion and the subsequent portions of the signal are interleaved.
9. An apparatus for acquiring a signal employing a coherent timebase, comprising:
a memory for storing a pattern length count times the samples per unit interval of a repetitive pattern in a signal to be acquired;
a strobe generator for providing strobes synchronous to a coherent timebase;
a controller for designating an arbitrary one of the data strobes as a timing for a potential trigger, and for counting a number of subsequent data strobes in accordance with the pattern length count times the samples per unit interval;
a signal acquisition module for acquiring a portion of the signal corresponding to the pattern length count times the samples per unit interval, beginning at a point in the signal defined by the designated arbitrary data strobe, and for acquiring one or more additional portions of the signal corresponding to the pattern length count times the samples per unit interval at a point in the signal defined by when the number of subsequent data strobes reaches the pattern length count times the samples per unit interval.
10. The apparatus of claim 9 , wherein the signal acquisition module acquires a portion of the signal each time the number of data strobes and subsequent data strobes reaches the pattern length count times the samples per unit interval.
11. The apparatus of claim 9 , wherein each time the controller counts data strobes up to the pattern length count times the samples per unit interval, a potential trigger is defined.
12. The apparatus of claim 11 , further comprising a trigger enable signal, wherein a portion of the signal is acquired when a potential trigger is reached, and the trigger enable signal is present.
13. The apparatus of claim 12 , wherein the trigger enable signal is input by a user.
14. The apparatus of claim 9 , wherein the portions of the signal acquired include digital samples.
15. The apparatus of claim 14 , wherein the digital samples acquired from the portion portions of the signal are interleaved.