摘要:
Activity on a digital communication network is divided into periodic intervals, that are further subdivided into first and second phases during which different classes of data are transmitted. A media access controller for a station on the network has an interface that connects to an external device which supplies first and second classes of data for transmission over the network. A first memory stores the first class of data and a second memory stores the second class of data. The external device supplies a third class of data that may be transmitted over the network during either the first or second phases. The third class of data is held in a third memory. A transmitter connects the three memories to the interface in order to send data over the network. A control circuit regulates the transfer of data from the memories to the transmitter, with data being transferred from the first memory when the media access controller has access to the network during one of the first phases. Data is transferred from the second memory when the media access controller has access to the network during one of the second phases, while data in the said third memory is transmitted when the media access controller has access to the network during either of the first or second phases. The transfer of data is governed by three pointers that indicate the amount of data within the memories that has been released for transmission by the device.
摘要:
Activity on a digital communication network is divided into periodic intervals and during a segment of each periodic interval a moderator station broadcasts a numerical count of the periodic intervals to all stations on the network. Each station has a memory in which a numerical value is stored, and a comparator that compares the numerical value to the numerical count received from the network. When the numerical count of the periodic intervals equals the numerical value, an apparatus within the station performs a defined operation, such as transmitting a message over the network or synchronizing a clock in the station to a master time standard. The equality of the periodic interval count and the numerical value also can be used to determine when to signal an external device. By using the count of the periodic intervals in this manner, the operation of several stations on the network can be coordinated.
摘要:
A digital communication network carries high and low priority data. The network stations that produce high priority data are assigned to a first group of stations and stations that produce low priority data are assigned to a second group with the two group not being mutually exclusive. Activity on the network is divided into periodic intervals of the same duration. Network control information, that defines how access to the medium, is determined is broadcast to all stations during a first segment of a periodic interval. The network control information defines the length of the periodic interval and of the periodic interval segments, and defines how many stations are in each group. Then during a second segment of the periodic interval, every station in the first group is afforded an opportunity, in a predefined order, to transmit high priority data over the medium. Stations in the second group are afforded an opportunity to transmit low priority data, when time remains after the first segment in a periodic interval before the network control information will be transmitted again. The specific station in the second group which is afforded an opportuinity to transmit first changes from periodic interval to periodic interval.
摘要:
A method is presented for fabricating an electrically isolated MEMS device having a conductive outer MEMS element, and an inner movable MEMS element spaced apart from the conductive outer MEMS element. The inner element includes a nonconductive base having a plurality of conductive structures extending therefrom. The conductive components are formed by plating a conductive material into a pre-formed mold which defines the shape of the conductor.
摘要:
A moderator on a communication network periodically transmits a set of parameters for a protocol that is used to communicate over the network. Each node on the network compares the set of protocol parameters from the moderator to a set of parameters stored in that node. If the sets of parameters at a given node do not match, that given node ceases transmitting messages over the network until either the set of protocol parameters from the moderator match the stored set of parameters, or a matching set of parameters is stored in the node. Typically the active node that is assigned the lowest numerical network address functions as the moderator. However, an automatic process is utilized to prevent a node with a non-matching set of the protocol parameters from becoming the moderator for more than a brief period of time. An override procedure is provided to force all the nodes on the network to adopt a common set of protocol parameters in the event that the automatic process fails.
摘要:
Each message carried by a communication network has a packet that contains data, a tag, and a generation count wherein duplicate packets sent in different messages have identical generation counts. A station includes a modem that connects to the communication network in order to receive messages. A fixed screener circuit has a first memory that stores a set of tag values and a fixed screener determines when a packet tag matches a tag value in the first memory. The station also has an interface through which tag values are received from an external device, such as a host computer. A general purpose screener includes a second memory with a plurality of storage locations in which to store tag values from the interface and a generation count associated with each tag value. A first comparator in the general purpose screener determines when a tag contained in a packet matches a tag value in the second memory, and a second comparator determines when a generation count in the packet matches the generation count in the second memory that is associated with the matching tag value. A control circuit produces a signal when the first comparator indicates a tag match and the second comparator indicates that the generation counts do not match. The station ignores the packet in the absence of the signal.
摘要:
A microelectromechanical system (MEMS) strain gauge includes at least one flexible arm that can be caused to oscillate. Transverse strain on the arm changes the resonant frequency of the arm. A detector communicating with the flexible arm may detect the frequency of oscillation to provide, an indication of the transverse strain of the substrate.
摘要:
Microelectromechanical (MEMS) switches are used to implement a flying capacitor circuit transferring of electrical power while preserving electrical isolation for size critical applications where transformers or coupling capacitors would not be practical. In one embodiment, the invention may be used to provide input circuits that present a programmable input impedance. The circuit may be modified to provide for power regulation.
摘要:
An interface circuit couples a host processor in an industrial control system to a local area communications network. In includes a protocol machine for receiving and transmitting messages on the network and an interface controller which is programmed to implement one or more protocols. As a message is received by the protocol machine, the interface controller anticipates a responsive message which it writes to the protocol machine even as the message is being received. If the message is received accurately, the responsive message is transmitted without delay.
摘要:
A method for fabricating an electrically isolated MEMS device having an outer stationary MEMS element and an inner movable MEMS element is provided that does not use a sacrificial layer. Rather, a pair of spacers are defined on the outer portions of the upper surface of a conductive wafer, and an insulating material is deposited thereon. The spacers are attached to a substrate to define an internal void therein. The wafer is then patterned to form the outer MEMS element as well as a conductive member for the inner MEMS element, separated from the outer MEMS element by a gap. A portion of the insulating layer that is disposed in the gap is then removed, thereby releasing the inner MEMS element from the stationary MEMS element.