Horology: time measuring systems or devices – Time interval – Electrical or electromechanical
Patent
1990-01-25
1991-10-15
Miska, Vit W.
Horology: time measuring systems or devices
Time interval
Electrical or electromechanical
368118, 324 731, 371 221, G04F 800, G01R 1512, G06F 1114
Patent
active
050580876
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for determining the electrical transit time of signal runs which are connected in each instance at one end to a terminal, e.g. for an integrated component, and which have at the other end a transmitter and a receiver.
Such a method is known for example from OSINGA/MAASKANT, "Handbuch der elektronischen Messgeraete" (Manual of Electronic Measuring Devices), 1984, pages 273 to 281, where measurements on transmission runs by the so-called "Time Domain Reflectometer (TDR) System" are described.
Automatic testers serve to check e.g. integrated circuits for absence of faults. To this end the automatic tester has connections, e.g. contact elements, into which the testpiece is plugged. Thereafter test signals are supplied to the testpiece from the tester, and the reply signals delivered thereupon by the testpiece are taken off and compared with nominal signals. Transmission of the test signals and of the reply signals occurs via signal runs, a signal run being connected to a terminal of the testpiece in each instance. Each signal run has a transmitter for the generation of test signals or respectively a receiver for the evaluation of the reply signals. Depending on whether the connection of the testpiece at a signal run is an output or an input, each signal run is operated in one or the other direction.
In testers for integrated circuits, in the ideal case all signal paths at the connecting point for the testpiece, also called testpiece interface, must have the same electrical length, that is, the signal runs involved in the test, having, for triggering (testpiece inputs), a formatting logic, driver, cables, etc., or, for reception (testpiece outputs), cables, a comparator, error logic, etc., should have the same electrical transit time, or should, under different load conditions, take into account the occurring distortion of the driver pulse edges and their passage through the circuit switching threshold of the testpiece. Since, however, the individual signal runs have a different transit time, the signals transmitted via the signal runs must be corrected. This process is called "deskewing". This correction can be performed by complex external measuring methods. For example, via an integrated relay switch matrix in conjunction with special drivers and comparator circuits, pulses can be fed to or taken off the testpiece interface, thus determining the transit time of the individual signal run. This method, however, is complex and does not take into consideration that also the additionally inserted circuits have a transit time.
It is the object of the invention to state a method wherein, without any great additional expense, a correction value for the case of reception can be obtained to correct different transit times of signal runs. In a method according to the preamble of claim 1, this problem is solved by the features of the characterizing part of claim 1.
Developments of the invention are evident from the sub-claims.
The advantage of the method according to the invention is that as additional element only a shortcircuit bridge is required, which is plugged in at the testpiece interface instead of a testpiece. The signal used for measuring the transit time is then automatically produced as central pulse by means of the existing signal runs whose transit time is not being checked, which (central pulse) has approximately the same form for all signal runs to be measured. If the occurrence in time of the output signal of the receiver is detected as a function of the central pulse, and this for all signal runs, relative values will result which characterize the different transit time of the transmission of signals from the interface via the signal runs to the receivers. By normalizing these values, e.g. to the lowest value, a correction factor can be obtained which can be made use of for the correction of the transit times over the signal runs and which causes the electrical conditions on the various transit time runs to be compensated.
The invention will be further explained with r
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"Inferred On-Chip Waveform Delay Measurement Technique", IBM Technical Disclosure Bulletin, vol. 28, No. 9, Feb. 1986, Armonk, N.Y. (U.S.), pp. 4048-4049.
Osinga/Maaskant: "Handbuch der Elektronischen", Messgeraete, 1984, pp. 273-281.
Vuksic Antun
Welzhofer Klaus
Miska Vit W.
Siemens Aktiengesellschaft
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