Boots – shoes – and leggings
Patent
1991-10-25
1995-02-21
Lee, Thomas C.
Boots, shoes, and leggings
364DIG1, 364271, 3642712, 375107, G06F 112
Patent
active
053924215
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
In certain applications it is important that the time of reception of a data. item is known. For example, this applies to open- and closed-loop control engineering where measurement data are used for controlling a process. The older a data item is, the worse it is as control data. In most cases, data can be processed quickly and effectively in the computer so that the delay becomes so small that it does not need to be considered. In these systems, it can be said that the data is provided with its time determination by the fact that the system is built up with a time delay which is so small that it can be neglected. In a system which works asynchronously with a data communication system, these transfer times can become long and undetermined in their length. Moreover, it is no longer a question of exact transfer times, but the transfer normally occurs with a certain time probability and with a certain spread based on what loading there is on the communication system and possibly what priority the message has. It is possible to organize the system with strict rules so that the transfer times are guaranteed. But this requires a well developed management which operates through all connected units. One of the reasons that a data communication system is used is to cut down on management, which is why this is a poor solution. Moreover, any reconfigurations require great expenditures. The best way to avoid management is to ensure that all units take into consideration the fact that the data comes randomly in time. For the units to be able to take into consideration variations in time, the receiving unit must know when the data is received in time or how much time the transfer of the data took. Moreover, if the position of the data in time is known, the receiving unit can check that the data has arrived within the arranged time frame. In the construction of a control system, it can be difficult to estimate and/or simulate all possible time delays, but these unexceptable delays can be detected with the aid of time information. At present it is uncommon for the position in time of the data to be included in process control, even in a system with a common clock where this is simple to carry out.
Time uncertainty is not unique to communication systems but also applies internally in a computer, for example a program can read an A/D converter every time it receives an interrupt. If this interrupt does not have the highest priority or a program has disabled the interrupt, it can take a certain time from the arrival of the data to when the data is processed in some program sequence. For this to function with a high accuracy, the data must be accompanied by the time when the data was received. In this way, the subsequent processing program can take into consideration the time of the data arrival. When different clocks are used, these must be synchronized so well that the error between them does not cause any problem for the program sequences which use the time as reference.
There are at least two reasons for ensuring the data position in time before it is processed. A better value than that which has been obtained can be extrapolated from earlier data through calculations. This extrapolation requires that the position in time for the given data is known for the calculation to have good accuracy. The program which will deal with the data can check that it has been received within the correct time. In the case where the data is old, new data can be requested, and in the worst case an error message can be given and/or the process terminated.
To obtain the time in a computer system, a resonant circuit constructed of coils and/or capacitors and/or crystals is used. Crystals are most common since they provide the best accuracy. With a crystal, a stable frequency is obtained which normally has an accuracy between .+-.25 and .+-.2000 ppm of the desired fundamental frequency. The error in the fundamental frequency occurs partly due to geometrical errors in the making of the crystal and errors which occur
REFERENCES:
patent: 4584643 (1986-04-01), Halpern et al.
patent: 4890222 (1989-12-01), Kirk
Patent Abstracts of Japan, vol. 10, No. 86, p. 443, Abstract of JP 60-222915, publ. 1985 Nov. 7 Fujitsu K.K.
IBM Technical Disclosure Bulletin, vol. 31, No. 6, Nov. 1988: "Distributed Clock Control and Synchronization," pp. 53 and 56.
IBM Technical Disclosure Bulletin, vol. 31, No. 7, Dec. 1988: "Synchronization of Remote Microcontrollers," pp. 71-72.
Faller Fran R.
Lee Thomas C.
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