Local communication system and frame forming comprising a programmable address generator for such a system

Abstract: In a local communication system a frame forming device (20,26,28) is provided which makes it possible to connect signal sources (10) that are designed to have a private connection to a destination device (16,28) (and therefore produce signals that are unspecific for selection of destination devices), via a shareable bus (25) to the destination device. To determine to which destination device a signal source is connected, the frame forming device contains an address generator (22). By making functions of the address generator programmable via the bus the system connections are made flexible.

Description: The invention relates to a local communication system, based on a shareable serial bus, for controlling a target device and comprising a signal source device for feeding a destination unspecific source signal to a signal input of a separately encapsulated frame forming device, the signal input being distinct from said bus, said frame forming device having an address generator for inserting a preprogrammed destination address into a source frame formed upon reception of said signal, said shareable bus interconnecting said frame forming device and said target device, wherein said target device has recognition means for recognizing a particular destination address within said source frame for subsequent action, and programming means for programming said generator. The invention also relates to a frame forming device for such a system. Such a system and frame forming device are known from EP 346614 A. It relates for example to a switch (the signal source device) which is physically separated from an electrical appliance (the target or destination device) it supposed to control, for example because the switch and the appliance are located at different locations in the building. Via a serial bus, source frames carrying messages composed of successive items of information are transmitted from one device to another. When such frames comprise, in series with other information, a destination address that determines a target device for which the frame is destined, the bus can be shared by more than one potential target device. The advantage of sharing is that only one connection is needed to couple all target devices and signal sources, thus reducing the overall number of connections needed for signal passing. Furthermore, adding devices or changing the logical connection pattern does not require a change of connecting wiring. In general, signal transfers can be performed without need to know the physical location of the signal source and destination device concerned. It is advantageous to use the bus also for coupling a conventional signal source device, such as a switch, to a destination device. Conventionally, for selective source-destination device communication, a separate private connection between each pair of source-destination device is used. Because of this, conventional signal sources produce destination unspecific signals, that is, if more than one appliance were connected to the source, a signal from the signal source would not discriminate between them; for example, a switch would affect all lamps connected to it. To connect such a source via a shareable bus, EP 346614 A teaches a frame forming device. The frame forming device, which serves as an intermediary between the signal source and the shareable bus, contains by itself the necessary intelligence for connection to the bus. Therefore, the signal source can be kept in its original form, that is, the signal source is separately encapsulated and can operate as if it is connected to a destination device entirely via a its own private connection. The frame forming device converts the unspecific signal, which it receives on a signal input, into a source frame. The address generator supplies the necessary destination address, determining to which receiving device the signal source is effectively connected. EP 346614 A also teaches a coordinating processor for remotely, that is, via the shareable bus, programming the address generated by the address generator. For this purpose it transmits programming frames comprising in the destination field a frame forming device address. The frame forming device comprises programming means, responsive to the programming frame from the shareable bus, for deriving a programming address from the content of the programming frame and programming the address generator with it. The known communication system has the disadvantage that a separate frame forming device has to be provided for each destination unspecific signal source. This makes the use of shareable busses in building, in particular in homes unattractive, both because of space needed and cost. It is, inter alia, an object of the invention to reduce the overhead required for connecting destination unspecific signal source devices. The communication system according to the invention achieves the object because it is characterized, in that said input accommodates a plurality of destination-unspecific but source specific signals from mutually distinct source devices, and said generator is discriminative among said signals with respect to their associated source device, for thereupon inserting said destination address as preprogrammed for the source device associated with the signal. Thus, the frame forming device is arranged for assigning one destination address selected from a plurality of addresses according to the source of the signal. In an embodiment of the communication bus system according to the invention characterized, in that the signal input comprises a plurality of external inputs, the generator being discriminative according to which of the external inputs the destination unspecific signal is fed to. In this way, assigning a destination address for the signal source only requires connecting it to an appropriate external input of the frame forming device. In another embodiment of the communication bus system according to the invention characterized, in that said generator is discriminative according to source identifying information inserted in the destination unspecific signal by the signal source device. Thus several signal sources may connected to a single input. In a further embodiment of the communication bus system according to the invention characterized, in that the signal source device comprises a further signal source device coupled to a further frame forming device coupled for feeding the signal input, the further frame forming device forming the destination unspecific signal in response to a further destination unspecific signal from the further signal source device, the further frame forming device being arranged for inserting the source identifying information, identifying both the further signal source device and the further frame forming device, in the destination unspecific signal. This provides an advantageous way for generating the source identifying information. In this way, the further destination unspecific signal can be forwarded from the further signal input, via the further shareable bus to the shareable bus. The generation of the destination address used on the shareable bus is localized in the frame forming device, which can be shared by many signal sources, which are distinguished by both the further signal source and the further frame forming device from which their signals arrive, i.e. the further signal sources are distinguished by the way they are connected to the system, rather than by any unique address. The invention also provides for a frame forming device for use in a communication system, in which for forming source frames for transmission on a shareable bus, the device comprising a signal input, distinct from said bus, for receiving a destination unspecific source signal, an address generator for inserting a preprogrammed destination address into the source frame which is formed upon reception of said signal, and programming means for programming said generator, characterized, in that said input is arranged for accommodating a plurality of destination-unspecific but source specific signals from mutually different source devices, and in that said generator is arranged to discriminate among said signals with respect to their associated source device, for thereupon inserting said destination address as preprogrammed for the source device associated with the signal. Such a frame forming device can be advantageously used to connect conventional signal source devices to a shareable bus. Under some circumstances, it may be desirable to avoid changes in connection during critical periods. For example, when a computer is transmitting a text to a printer in a series of successive source frames via a frame forming device, it would be undesirable to have the destination address, and hence the printer changed halfway. To avoid this one embodiment of the local communication device is characterized in that the local communication system comprises the programming means are arranged to be responsive to a programming frame received from the shareable bus. Blocking and programming may be combined into one command if erasure of a programmed address is provided for; thus, after it is programmed, a connection is not accessible to accidental reprogramming before it is erased. These and other attractive features of the invention will be described by means of a number of figures, of which figure 1 shows a signal source and a destination device connected by a private connection figure 2 shows a communication system connecting a signal source and a destination device via a bus figure 3 shows a frame for transmission via a serial bus figure 4 shows a communication system with a bus programmable address generator figure 5 shows a frame forming device with blocking means figure 6 shows a communication system with selection means for selecting a programmed address figure 7 shows a communication system with a gateway between two busses. Figure 1 depicts a circuit in which a signal source 10, has its output 12 connected to an input 14 of a destination device 16 via a connection 18. The figure abstracts common situations, such as when a switch 10 controls a lamp 16, or some other eletrical appliance 16. In another example, the signal source 10 is a computer and the destination device 16 is a printer. Usually, such signal sources produce destination unspecific signals, that is, these signals are not capable of selecting a specific destination device in case that more than one destination device 16 is coupled to the connection 18. For example, a switch would control all lamps connected to it. Figure 2 shows a communication system for realizing an equivalent connection between a signal source and a destination device via a bus 25. Here too the signal source 10 is connected to the destination device 16. The important difference is that the bus is shared with another destination device 28 also connected to the bus. To make an effective connection only to a selected device 16 and not to another device 28, signals over the bus carry information in the form of frames. Figure 3 depicts a frame. In the frame, information bits are in a time sequence, for example as a binary signal across two wires. In the frame, there is a field 30 (a period of time) for coding a destination address, and one for coding information (32). An example of the use of frames in a bus system called the D 2 B system can be found in US-A-4429384. In D 2 B frames also contain a source address 34, which is not essential in the present case. Returning now to figure 2, the communication system comprises a frame forming device 20 which is provided for forming a frame in response to a signal received from the output 12 of the signal source 10. In the present system, the intelligence required for this response is concentrated in the frame forming device. The signal source remains unmodified as compared to figure 1, still producing destination unspecific signals at its output 12. The frame forming device 20 contains circuitry 24 for generating appropriate signals for handling protocol on the bus. An example of such a protocol handling can be found in the D 2 B publication cited above. To fill in the content of the destination address field 30, the frame forming device 20 comprises an address generator 22. The address which this address generator 22 generates is programmable. In one implementation it is for example stored in a memory. This memory is preferably novolatile (e.g. magnetic or an EEPROM), once an address is stored, each time the frame forming device 20 forms a source frame in response to a signal on the output 12, the stored address is read out and inserted in the destination field 30 of the source frame. This frame is then transmitted via the bus 25. Suppose that the destination address of the frame corresponds to a destination address set on an address setting 27 of a receiving station 26 connected to the bus. In that case, the receiving station 26 will pass the information content of the signal to the destination device 16. The destination device 16 may also be unmodified, that is, intended for a direct connection 28 as in figure 1, without means for receiving frames from a bus. However, it is also possible that, like the other receiving device, 28 is designed specifically for use on a bus and contains means for receiving frames itself. With several measures that will not add very much to its complexity the frame forming device can be made to provide greater flexibility to a communication system as in figure 2. These measures involve flexibility in programming and controlling the address generator. In figure 4, several such measures are shown. For one thing, the frame forming device 20 comprises programming means 40. The programming means 40 themselves are activated via the bus 25, by a programming frame. Such a programming frame will have a destination address corresponding to the programming means and a content from which the address which is programmed into the address generator 22 can be derived. When it is desirable to reprogram the address generator, for example if the signal source is a push button at the door of a building and it must be connected to an alarm device in a specific room, (for example because the person for whom the alarm is intended moves to that room), this can be achieved by sending an appropriate programming frame via the bus: no extra wiring is needed for programming and no one needs to go to the push button (or its frame forming device) to program it. The programming frame itself may originate from any transmitting station connected to the bus 25. For example, it may originate at a coordinating processor (not shown). After programming, the connection no longer requires any attention from the coordinating processor and is indifferent to failure of this processor. In some applications, it is desirable that a signal reaches a plurality of receiving stations. For example, a push button at the door might be connected to a plurality of alarm devices, or a light switch to a plurality of lamps. In these applications, it is desirable that the frame forming device can store a plurality of programmed addresses 42, one for each destination device. In reponse to the signal at the output 12, the frame forming device will send a pluralitity of source frames, each programmed address being contained in at least one of the frames. In one embodiment of the invention, one such frame may contain more than one of the programmed frames. In the preferred embodiment, each of the plurality of source frames contains just one of the plurality of programmed addresses, notably as destination address. In other applications, it is desirable to disconnect a destination device 10 from the source device 16, for example, to disable a push button at the door. In principle, this can be achieved by programming an unused address, because this way source frames will not have any effect. However, this entails transmitting unneccessary messages on the bus, and does not account for the fact that in some applications it is desirable for the frame forming device to wait until an acknowledgement is received from the destination device, and to retry transmitting the frame if it is not acknowledged. Therefore, another embodimnent of the invention involves not sending a source from at all. For this purpose, the frame forming device 20 must have address erasure means 44 for erasing a programmed address, and means for preventing the transmission of source frames if an addres is erased. The erasure means 44 might be activated by a reset button at the device, but it is also possible to provide for control by a frame via the bus. Figure 5 shows a further elaboration of the frame forming device 20. In this figure blocking means 50, for blocking the programming means 40 and, if present, the erasure means 44 have been added. The idea is that, upon reception of a blocking frame, the blocking means prevent reprogramming of the address generator 22 by the programming means. Later, the blocking can be removed after reception of an unblocking command. A purpose of blocking is to freeze the connection pattern of the frame forming device. For example, if the destination device 26 is a printer and the signal source 10 is a computer issuing printing commands which are transferred in successive frames to the printer 26, it would be undesirable that the destination of the frames is changed halfway, in between these successive frames. The blocking means serve to prevent this. Most often, it will be sufficient to combine the blocking function with the programming function: reprogramming will be blocked automatically after programming until the programmed addres is erased. The frame forming device can also be made more flexible by letting the signal source influence the address generator. Figure 6 shows an example of this. In this figure, the frame forming device 20 comprises selection means 60 and a plurality of stored addresses 62. The selection means 60 are capable of selecting any one of the stored addresses 62 for insertion as destination address 30 in the source frame. The selection of the storage location is in this case controlled by the signal source 10. In one example, the frame forming device has a plurality of inputs, the input at which a signal appears determining which storage location 62 is selected. In this way, one frame forming device 20 does the work of a plurality of separate frame forming devices for separate signal sources 10, with a corresponding saving on overhead. In another example, a plurality of signal sources 10 is collectively connected to a single input of one frame forming device. In this case, it is neccessary that the signal source 10 can be identified from its signal, for example because the signal contains a source address. In this way a source specific, but destination unspecific signal is converted into a destination specific frame via a programmable "mapping" storage 62. This embodiment can advantageously be used in a recursive application of the invention. In figure 7 the receiving device is replaced by a further frame forming device 20 connected to a further bus 25 and to a further receiving device 16. In this case, the address generator in the "old" frame forming device 20, does not need to store the destination address of the further receiving device 16 beyond the further frame forming device, because this address will be generated by further selection means 60. When the source frame transmitted by the original frame forming device 20 comprises a source identification characteristic of this frame forming device 20, such as for example a source address, the further selection means 60 will select a further destination address under control of this source identification. This recursive application can be repeated indefinitely, adding further busses etcetera, provided each frame forming device arguments the frame with its own identification. The alternative to this approach would be to store the full destination address (i.e. the addres of the further frame forming device 20 and the further destination device 16) in the original frame forming device 20. The advantage of the recursive approach is that the destination information is distributed, which reduces the intelligence required in the original frame forming device 20 because it now needs no knowledge of the further bus 25. In another embodiment of the invention, the selection means 60 are controlled by the type of signal produced by the source 10. For example, the message might be from one of the following types: control signal, status signal, error signal. By letting the type control the destination, for example error signals may go to a different destination than control signals, as determined by the programming of the plurality of destination addresses 62. Although in the preceding various measures in the frame forming device 20 have been shown as implemented through separate units, it shall be clear that such things as address separation, frame forming, programming, erasing, blocking, selection etcetera can also be implemented in a single processor capable of interfacing to the bus.

Claims: A local communication system, based on a shareable serial bus (25), for controlling a target device (26,28) and comprising a signal source device (10) for feeding a destination unspecific source signal to a signal input of a separately encapsulated frame forming device (20), the signal input being distinct from said bus (25), said frame forming device (20) having an address generator (60,62) for inserting a preprogrammed destination address into a source frame formed upon reception of said signal, said shareable bus (25) interconnecting said frame forming device (20) and said target device (26,28), wherein said target device (26,28) has recognition means for recognizing a particular destination address within said source frame for subsequent action, and programming means (40) for programming said generator (60,62), characterized, in that said input accommodates a plurality of destination-unspecific but source specific signals from mutually distinct source devices (10), and said generator (60,62) is discriminative among said signals with respect to their associated source device (10), for thereupon inserting said destination address as preprogrammed for the source device (10) associated with the signal. A local communication system according to Claim 1, characterized, in that the signal input comprises a plurality of external inputs, the generator (60,62) being discriminative according to which of the external inputs the destination unspecific signal is fed to. A local communication system according to Claim 1, characterized, in that said generator (60,62) is discriminative according to source identifying information inserted in the destination unspecific signal by the signal source device (10). A local communication system according to Claim 3, characterized, in that the signal source device comprises a further signal source device (10) coupled to a further frame forming device (20) coupled for feeding the signal input, the further frame forming device (20) forming the destination unspecific signal in response to a further destination unspecific signal from the further signal source device (10), the further frame forming device (20) being arranged for inserting the source identifying information, identifying both the further signal source device (10) and the further frame forming device (20), in the destination unspecific signal. A frame forming device for use in a local communication system according to any one of the claims 1 to 4, for forming source frames for transmission on a shareable bus (25), the device comprising a signal input, distinct from said bus, for receiving a destination unspecific source signal, an address generator (60,62) for inserting a preprogrammed destination address into the source frame which is formed upon reception of said signal, and programming means (40) for programming said generator, characterized, in that said input is arranged for accommodating a plurality of destination-unspecific but source specific signals from mutually different source devices (10), and in that said generator (60,62) is arranged to discriminate among said signals with respect to their associated source device (10), for thereupon inserting said destination address as preprogrammed for the source device (10) associated with the signal. A frame forming device according to Claim 5, characterized, in that the signal input comprises a plurality of external inputs, the generator (60,62) being discriminative according to which of the external inputs the destination unspecific signal is fed to. A frame forming device according to Claim 5, characterized, in that said generator (60,62) is discriminative according to source identifying information in the destination unspecific signal. A frame forming device according to Claim 5 or 6, characterized, in that it comprises means for inserting source identifying information, identifying both the signal source device (10) and the frame forming device (20), in the destination unspecific signal. A frame forming device according to Claim 5, characterized, in that the programming means (40) are arranged to be responsive to a programming frame received from the shareable bus (25). A frame forming device according to Claim 9, characterized, in that it comprises blocking means (50), responsive to reception of a blocking frame from the shareable bus (25), for blocking said programming.

Inventors: GOEERTZ HENDRIK MARIE HUBERTUS, GOEERTZ, HENDRIK MARIE HUBERTUS GERARDUS, Göertz, Hendrik Marie Hubertus Gerardus
Applicants: PHILIPS ELECTRONICS NV, PHILIPS ELECTRONICS N.V.
Application year: 1991
Main classification: H04L12
IPC codes: H04Q9, H04L12