U.S. Philips Corporation

Koninklijke Philips Corporation N.v.

Robert Mores

Harald Eisele

Peter Fuhrmann

Wolfgang Otto Budde

Patrick Willem Hubert Heuts

Aloysius Johannes Maria Boomkamp

Egon Johnk

Peter Buhring

A CAN communication line is operated whilst detecting a ground level shift on the communication line through storing a data element indicative for the shift. In particular, a current line voltage level is compared to a standard level, and a thresholded version of the comparison is fed to a storage element that is triggered by a local transmission indicator signal. Then a ground shift sample bit from the storage element is outputted.

Station and method for operating a CAN communication line

The invention relates to a communications network () comprising a plurality of network nodes (), which include each a synchronization circuit () for generating a global clock signal (GT) from a local clock signal (LT) formed by a clock generator () in dependence on a time of reception of a message. The synchronization circuit () includes a divider arrangement () for dividing the local clock signal (LT) in dependence on a correction term (KT) and at least one divider factor which is produced by a scaler arrangement (). The comparator circuit () is provided for forming the correction term by comparing the instant of reception of a message and of the local clock signal LT. Furthermore, the synchronizing circuit () includes a divider control () which may perform a change of at least one divider factor when the correction term (KT) exceeds a predefined first threshold.

Communications network having a time-controlled communication protocol

In an electronic system for the transmission of data between a number of stations, sub-system operation can be achieved by a suitable choice of signal levels and wake-up levels, so that some of the stations can communicate with one another while other stations are in a sleep mode in which power is saved.

System for the transmission of data

A sub-net operation with increased availability and reduced power consumption is achieved in a bus system with a plurality of stations ( ) which are coupled to one another via a system of conductors ( ). Each of the stations includes a transceiver ( ) and a control unit ( ). The stations are switched from a quiescent state to a standby state in response to the reception of a first wake-up signal and selected stations are switched to a normal operating state upon reception of a second wake-up signal, whereby stations are selected.

Data transmission system

In a system for the transmission of logic levels via a bus the recessive level, being of higher impedance in comparison with the dominant level, is not adjusted by means of a resistor but by means of a termination arrangement with three break points in the current/voltage diagram. In the third quadrant of the current/voltage diagram this termination arrangement has a resistance which is higher than that of a lead terminated by means of a linear resistor. In the first quadrant the rise of the characteristic up to a voltage below a receiving threshold is steeper than in the case of termination by means of a resistor. Subsequently, in the first quadrant the characteristic is subject to a current limitation which is effective from a voltage below the receiving threshold to a value beyond the working point of the dominant driver. Beyond the working point of the dominant driver the current limitation is removed again, so that the rise is steeper than in the case of termination by means of a resistor. This termination arrangement optimizes the ratio of the value of the driver currents, and the associated radiation via the bus, to the speed at which a level is adjusted on the bus. Moreover, the tolerance in respect of ground offset is thus improved and also the resistance to radiation.

Circuit arrangement for bias adjustment of bus levels

Generally speaking, steep signal edges are required for the processing of digital signals; however, notably externally supplied signals which are conducted, for example, via long cables are liable to have comparatively flat signal edges. By selecting appropriate switching thresholds, delays between an input signal and an output signal of a circuit can be minimized. The circuit selects the first switching threshold at a low value of the input signal and switches the first threshold value to a second, higher threshold value when the input signal exceeds a further, higher threshold value. Thus, an output signal is generated comparatively quickly after the beginning of the positive-going or negative-going edge of the input signal. This can be realized by switching over the switching threshold of a comparator or by utilizing two comparators. Switching over to the various switching thresholds, or the various comparators, is provided by a further control circuit which may also be driven by the comparators themselves. A particularly high insensitivity to interference is achieved when use is made of two comparators which themselves are constructed as Schmitt triggers.

Accelerated switching by selection of various threshold levels

Power and data are both transmitted over a single transmission line to which a power source and a number of stations are connected. A bipolar AC voltage is supplied to the line by the power source, the half cycle pulses of one polarity being used for supply of power only, while transmission of data is achieved by modulation exclusively of the half cycle pulses of the other polarity. High power is supplied to the stations by providing pulses of the one polarity at a low ohmic level. Only low power is required for modulation for the purpose of data transmission, and so the pulses of the other polarity are supplied at a relatively high ohmic level. Thus, only two conductors are required, one of which can be replaced by the system ground in the simplest case. If three conductors are provided, it is possible to achieve improved tolerance of defects in a conductor. At least parts of the system are maintained in operation, in the event of a short-circuit, by providing separation units which automatically disconnect different segments of a short-circuited line and automatically reconnect them after the short-circuit has been eliminated.

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Hamburg, Germany

Robert Mores