Bus system and method for operating the same

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BUS SYSTEM AND METHOD FOR OPERATING THE SAME nrfwdn1? no'wi D'sny

Eitan Law Group

Eitan, Mehulal, Pappo, Kugler

P-9959-IL

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I, David Char Is ton, MMus, BA, MIL, MITI, Dipl. Trans., of 26 Castleford Rd,

Ludlow, Shropshire, SY8 IDF hereby certify that to the best of my knowledge and belief the following is a true translation made by me of the text of PCT Application No. PCT/EP2006/001161

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Dated this day of 2006 .&gt;»· 1

Translation of PCT/EP2006/001161

Bus system and method for operating the bus system 5 The present invention relates to a bus system, especially a Serial Radio Controlled Bus (RCBSER) for controlling, for example, external antenna-tuning units, amplifiers and filters etc. in real time. 10 In a serial bus system, message processing based on a stored communication of messages is a standard procedure. The messages are communicated from bus node to bus node, wherein the messages of the currently-processing bus node are treated preferentially. With this type of node-related 15 communication of messages, a real-time capability cannot be provided, because the dwell time of a message in the memory of the bus nodes is unpredictable and can, at the very most, be indicated statistically. 20 By contrast with synchronous buses, in which a certain portion of a synchronous channel is assigned to a special node· for a certain time, an asynchronous control allows the communication of several requests for small data quantities, without the need for an interruption of the message 25 transmission. Documents US 5,719,858 and EP 1 465 370 A1 propose systems, which allow an asynchronous transmission on the basis of a synchronous physical channel. Accordingly, it is possible to provide an environment for communication between two nodes, which also satisfies stringent 30 requirements with regard to time conditions. For example, in the case of US 5,719,858, several nodes are connected to a TDM (time division multiplexed) bus, on which a certain bandwidth is made available to several bus nodes. This is then distributed to the individual units using a time-slice method. In the case of EP 1 465 370 Al, a data telegram is subdivided for asynchronous processing and packed into so-called "clocked frames", so that it is possible to allow a synchronous data transmission on a synchronous bus.

The Manchester coding method has been established as the standard method for bus systems. It is simple to implement, direct-current-free and allows the auto-synchronisation of stations communicating with one another, so that a separate clock-pulse supply is not required.

The object of the present invention is to accelerate the communication in a bus system thereby improving its realtime capability.

This object is achieved by a bus system with the features of claim 1 and a method with the features of claim 11.

In the serial bus system, bit information can be exchanged between units in real time via a synchronisation signal, and in parallel to this, messages of greater length can be communicated in an asynchronous manner.

Within this bus system, a central bus node or a specifically-marked bus node is defined as the superordinate unit, which is connected via a bus to several other bus nodes, defined as the subordinate units, through which it communicates .

In particular, synchronisation signals, with which time-critical signals are transmitted from unit to unit, are constantly exchanged between the individual units. In parallel to this, messages of a finite length can be transmitted or exchanged between the individual units asynchronously and completely independently of the synchronisation signals.

Advantageous further, developments are specified in the dependent claims.

It is already known that a header, which, in the present case, allows the receiver to be synchronised for the reception of a message, can be attached to data telegrams within message systems in addition to the address and data information. A telegram of this kind is represented in the realisation described below, for example, by 24 fields, wherein 13 fields are used for address information and 8 fields for data. The 13 fields for address information refer not only to the addresses of the individual subordinate units, but also determine the parameters addressed or to be modified within the respective supplementary device.

The header of the message indicates not only the beginning of a message, but is used for the synchronisation of the units. This character sequence, also referred to as a synchronous word, allows the receiver to recognise the beginning of the subsequent data word.

To allow an initial synchronisation between the individual units, a so-called synchronisation frame is first transmitted. This ensures the mutual calibration of a common

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clock pulse and the assignment of the fields of a message to their coding. If no messages or data telegrams are transmitted, synchronisation frames are constantly transmitted from one unit to the next unit. These also ensure the synchronisation of the clock-pulse generators.

The exchange of information in real time is based upon the constantly-exchanged bit signal or clock-pulse signal between the individual units. The initial transmission of 10 the synchronisation frame specifies the assignment of a character 'X' to '0' or '1' and Ύ' to '0' or '1'. This information is communicated to all units on the serial bus system, so that the same signal is transmitted on all connecting lines. If one unit wishes to transmit a bit 15 message to the superordinate unit, this changes the assignment 'X' to '0' or '1' and/or Ύ' to '0' '1'. In the subsequent unit, this signal is combined in an AND element with its own clock-pulse signal to form a combined signal and transmitted to the unit disposed in the next highest 20 position. In this manner, a bit signal can be transmitted very rapidly from unit to unit and to a master. A data packet, which is independent of the bit information, is distributed bit by bit to intermediate bit positions so that data packets are transmitted in an asynchronous manner 25 alongside the clock-pulse signal. Accordingly, it is possible to speak of channels, in which, on the one hand, bit information can be exchanged constantly in real time and, on the other hand, a relatively long message can be transmitted asynchronously with time distribution. 30

Moreover, the real-time capability is further provided in that the bit information is not placed in intermediate storage. The bit signals are combined in the units as a continuous signal by an AND linking with the internally- generated bit signal and implemented without delay. Data telegrams must initially be extracted and read into a memory in their full length in order to be interpreted.

The use of the differential Manchester code allows the fields to be presented with one bit each so that the resulting message length is 48 bits, and the length, of the data and address information is specified as 8 and 13 bits respectively. The deviations from the generally-used method of coding introduced here, allow the definition of further characters, which, for their part, allow the definition of further control characters. By way of deviation from a standard alphabet, which contains the characters 'K', 'J', '0' and '1', 'READY', 'TX_ACTIVE' and 'CARRIER_MAGNITUDE' can be created through the additional characters or control signals 'X' , Ύ' .

In order to communicate the messages in the subordinate units connected sequentially, for example, via coaxial or optical-fibre cable, a memory is provided in each of the supplementary devices, in which messages are placed into intermediate storage before they are communicated, thereby guaranteeing a controlled message transmission from subordinate unit to subordinate unit. Additionally, a corresponding logic unit provides the means for processing the messages within a subordinate unit or for transferring a message to another subordinate unit. The memory and logic unit are realised, for example using "programmable gate arrays" (FPGA-component) in the devices, thereby allowing future requirements for the performance capability of the bus to be taken into consideration.

Providing the integrated memory and the logic unit, achieves a communication procedure for handling standard messages and time-critical messages of the following type: 1. ) If a subordinate unit receives a message, a check is first carried out to determine whether the internal memory already contains a message. If the memory contains a message, the incoming message is entered in the memory and only communicated, if all previously-received messages or messages entered in the memory have been communicated to the subsequent subordinate units or removed from the memory. 2. ) If a message is received from a subordinate unit and its memory is empty, the message is communicated directly. 3. ) If a time-critical message is received from a subordinate unit, the status of the memory is not checked, but an internal status is directly verified, and the message is communicated only after this. 4. ) If a TX_ACTIVE or TX_ACTIVE/CARRIER_MAGNITUDE message is received from the superordinate unit, the setting of the subordinate unit is no longer changed, and an internal status is set. After the reception of a message from a preceding, subordinate unit, this is immediately communicated to the subsequent subordinate unit.

With this general message infrastructure, it is possible to provide a basic functionality, in which individual

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10 subordinate units, which are connected to the terminals of the bus, communicate with a superordinate unit via a serial bus. In this context, a reply message regarding the successful adjustment of parameters can be given, or the status of the subordinate units or values such as temperature can be communicated to the superordinate unit. The transmission of bit information via the constantly-exchanged clock-pulse signal additionally allows the rapid exchange of an information unit in real time.

The invention is described in greater detail below with reference to the drawings. The drawings are as follows: 20

Figure la shows the structure of the serial bus; Figure lb shows the structure of a subordinate unit; Figure 2 shows an , application of the bus; Figure 3 shows the standard message structure; Figure 4 shows the message structure for rapid 25

Figure 5

Figure 6

Figure 7a transmission of messages; shows the differential Manchester code; shows the time behaviour of a message for rapid transmission on the bus; shows the message exchange between subordinate units in a first phase; 8

Figure 7b shows the message exchange between subordinate units in a second phase; 5 Figure 8a shows the message exchange for rapid transmission on the bus in a first phase; Figure 8b shows the message exchange for rapid transmission on the bus in a second phase; 10 Figure 9 shows the message exchange for rapid transmission on the bus in a third phase; Figure 10 shows special time-critical messages; 15 Figure 11 shows the time behaviour of a message transmission in a first phase and 20 Figure 12 shows the time behaviour of the message transmission in a second phase.

The structure of the bus system 1 illustrated in Figures la and lb is characterised by a superordinate unit li, to which several subordinate units 12, I3 can be connected. The subordinate units 12, I3 are connected in series to form a 25 series structure. In this context, a first subordinate unit UE4, for example, a pre-selector, is connected via two cables to a superordinate unit i)E, for example, a radio device, and after that, a second subordinate unit UE3, for example, a standing-wave measuring instrument, is connected 30 via another two cables to the first subordinate unit and so on. A final subordinate unit UE1, for example, an antenna tuning unit (ATU) terminates the bus 15.

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Optical-fibre cables and optical connectors can be used for the cabling 14 instead of coaxial cables. Although the bus system 1 is primarily designed for controlling external modules, the concept described below is also suitable for applications, which require the control of internal modules. By way of simplification, the abbreviation RCBSER is also used to describe the bus 15. It must also be mentioned, that each device unit lx, 12, and respectively 13 has at its disposal, for example, a programmable gate array (FPGA component), which contains a memory 1211 and controls communication via the bus.

One application of the bus system 1 illustrated in Figure 2 15 provides the structure of a radio system. In this context, the superordinate unit 1χ, the radio device 2X and the subordinate units 12 can be supplementary devices 22 such as amplifiers, standing-wave measuring instruments or selectors, which are connected to the radio device, for 20 example, via coaxial and/or optical-fibre cables 24. The bus system 1 is terminated, for example, by an automatic antenna-tuning unit (ATU) 23.

As shown in Figure 3, the standard telegram 3 consists of a 25 message header 33, which is formed by a start bit 'K' followed by a start bit 'J' and a subsequent status bit. The status bit is defined either with the character RD/WR_RF or IRQ_RF_EXT, depending upon whether the transmission is implemented from the superordinate unit to the subordinate 30 units or in the opposite direction. This is followed by an address field 3χ and a data field 32. In the message 10 structure shown by way of example, 13 bits are used for the address field and 8 bits are used for the data field.

Figure 4 shows the bit-wise subdivision of a message in the free positions between the clock-pulse bits or characters. The clock-pulse signal is recognisable as an alternating sequence of characters 'X' and Ύ'. As will be described below, a differential Manchester code is used by preference for the coding of the characters. In this context, the character 'X' is recognisable in that it appears between the first and second start or synchronisation bit 'K' and 'J'. The character Ύ' follows the start or synchronisation bit 'J'. As a result of this bit-wise subdivision of the message, it is possible to exchange bit information simultaneously and completely independently on the serial bus alongside messages transmitted asynchronously between the units. The alternating insertion of the characters 'X' and Ύ' can be immediately evaluated. The bit information, which is transmitted via the constantly-exchanged clock-pulse signals, is also indicated as a time-critical signal.

Figure 5 shows the structure of the preferred Manchester coding method 5. According to the method 5, a subdivision into bit cells takes place, wherein a different polarisation or amplitude is indicated in the first half of the bit cell by comparison with the second half of the bit cell. This means that an abrupt change of level occurs in each bit cell, which also allows, for example, a simple synchronisation of the participating stations. The differentiation of the characters takes place in this context through an edge at the start of the bit. For example, the character '0' is characterised by an edge at 11 the start of the bit, whereas no edge is coded in the case of the character '1'. According to the present, preferred derivative of the Manchester code, two code extensions 'K' and 'J' are additionally adopted in the code alphabet, that 5 is to say, within the quantity of characters used. In this context, the code extension is given in that no change of polarisation or abrupt change of level occurs in the middle of the bit. The character 'K' is characterised by an edge; the character 'J' by 'no edge' at the beginning of the bit. 10

Figure 6 shows the time behaviour or timing 6 of a message telegram, in particular, also of a time-critical message telegram 4. With an exemplary data rate of 12.5 MHz, there is a time allocation of TB = 80ns per bit and accordingly 15 for the entire length of a time-critical telegram TM = 3.84ps (= 24 x 80ns). This provides a tolerance band of 1% for the safe processing of the messages.

Figures 7a and 7b show the standard message processing. 20 Figure 7a shows the processing of standard messages, which are processed using a memory I211.

Standard messages 3 from the superordinate unit 1χ to the subordinate units 12 and/or 13 are received simultaneously 25 by the subordinate units 12 and/or 13. This message communication is described as a point-to-multipoint connection .

Standard messages 3 are communicated from the subordinate 30 units 13 to the superordinate unit 13 via the intermediate subordinate units 12. This achieves a smooth running of message communication from one subordinate unit 12 and/or 13 12 to the superordinate unit 1χ on the serial bus 15. Access problems do not occur, because the bus I5 is structured in the direction towards the centre 1χ in such a manner that in the short-term, a so-called point-to-point connection is set up respectively between two subordinate units 12 and/or one subordinate unit 12 and the superordinate unit 1χ until a message 3 has been successfully communicated to the superordinate unit 1χ.

Two approaches are possible for processing a standard message 3. Figures 7a and 7b illustrate the method of functioning. Figure 7a shows a first case, in which a subordinate unit UEn receives a message Νχ from a subordinate unit UEn-1 via a point-to-point connection and, represented by a message N2, checks whether its own message memory 1211 is empty. If this is the case, a message N3 is communicated directly to the memory of the subsequent subordinate unit UEn+1.

Figure 7b shows a second case. If the memory 1211 already contains at least one message, the received message N4 is stored in the memory 1211 until the successful processing of all messages contained in the memory 12χχ, and only after the processing of the messages in the memory is it communicated as a message N6 to the subsequent subordinate unit UEn+1.

The dwell time of the message N4 in the memory 1211 depends upon the initial number of messages in the memory 12χχ.

Time-critical signals 4, of which the processing is illustrated in Figures 8a and 8b, are transmitted if a separate processing and a rapid exchange of messages in the form of bit information are required and possible. This 13 occurs, for example, if, as a superordinate unit t)E for the transmission of a high-frequency signal to the subordinate units UE1-UE4, a radio device transmits given settings, for example, amplification factors, filter parameters or settings of an antenna tuning unit, and, shortly before the beginning of the transmission, requests a confirmation regarding the successful setting of the necessary parameters, so that it can then transmit the high-frequency signal. The confirmations are then transmitted in the form of a time-critical signal 4 from the subordinate units UE1-UE4 to the superordinate unit 0E. This takes place in such a manner that the last element UE1 of the bus 15 is the first to change the coding of its clock-pulse signal. By contrast with standard messages, time-critical signals are processed separately in the subordinate units, through which they pass.

Figure 8a shows a first general method of presentation. If a time-critical signal 4, indicated in Figure 8a by reference N7, of the preceding unit UE2 arrives at the subordinate unit 12 as a result of a preceding message for the high-frequency transmission of the superordinate unit to all or only some of the subordinate units UE1-UE4, for example, to the subordinate unit (JE3, an internal status READY is initially checked, and the signal 4 is then transmitted as a time-critical collective message Ng to the subsequent subordinate unit UE3 or in the case of the last subordinate unit UE4 to the superordinate unit t)E.

Figure 8b shows the processing in the event of the special TX_ACTIVE signal 10i, which refers to an imminent high-frequency signal transmission. In this variant, a READY 14 signal 103 is expected by all subordinate units UE1-UE4 and this is communicated, for example, from subordinate unit UE3 to subordinate unit UE4 and then communicated to the superordinate unit UE.

In this context, the communication takes place in such a manner that the superordinate unit UE transmits a signal N9 to a subordinate unit UEn. This sets an internal status to READY and waits for a signal N10 from a preceding subordinate unit UEn-1 in the bus 15. After interrogating the internal status, a combined signal Nxx is then transmitted to a subsequent subordinate unit UEn+1.

Figure 9 shows a further signal-processing procedure. A signal NX2 from a superordinate unit UE is received by a subordinate unit UEn. When using the bus 15, this refers to the reception of a TX_ACTIVE/CARRIER_MAGNITUDE signal, which characterises the direct transmission mode. Following this, an internal status is optionally set, which is not shown in the drawings. After this, if a signal NX3 is received from a preceding subordinate unit UEn-1, a signal NX4 is generated and communicated to a subsequent subordinate unit 12.

Figure 10 shows three special signals, in particular, time-critical signals 10x, 102, and 103, which are transmitted from the superordinate unit UE to the subordinate units UE1-UE4 and from the subordinate units UE1-UE4 to the centre UE. In this context, a first signal 10x from the superordinate unit UE to all subordinate units UE1-UE4 is characterised in that, as a clock-pulse signal, it is coded as a constant sequence of characters 'X'. Figure 10 shows once again the parallel exchange of real-time bit information and 15 relatively long data packets. The character TX_ACTIVE is characterised in that it is transmitted as a signal 10χ from the superordinate unit UE to the subordinate units UE1-UE4. A second signal IO2 from the superordinate unit t)E to the subordinate units UE1-UE4 is also communicated using the clock-pulse signal. However, TX_ACTIVE and CARRIER_MAGNITUDE are transmitted in alternation. In this context, CARRIER_MAGNITUDE is transmitted as Ύ'. A preceding sync frame once again ensures a calibration of the clock-pulse generators. In the case of a READY signal IO3 from the subordinate units UE1-UE4 to the superordinate unit t)E, a READY signal is transmitted as described above.

In the form of time diagrams, Figures 11 and 12 show an overview of the time course of the bus activity for communicating time-critical signals via the connected subordinate units UE1-UE4 through to the superordinate unit ϋΕ on the bus 15. After a request of the superordinate unit ϋΕ of the length TM and a predetermined response time of the final or terminal subordinate unit UE1 on the bus, the signal regarding the conclusion of the parameter settings in the subordinate units is communicated according to the point-to-point signal-processing method described above from subordinate unit UEn-1 to subordinate unit UEn and finally to the superordinate unit UE. The total response time is then obtained as shown in Figure 11. Figure 12 shows the conditions for the case, in which a full message duration is required for the evaluation of the internal status.

The invention is not restricted to the exemplary embodiment described. The bus system according to the invention can be 16 used in many different ways. All the elements described and indicated can be combined with one another as required. □’Ewan , crnxan rw:n ατα inia^a pnow pnszn irn nr -jaoa ,ρνιη ηχΰ- paoana ma™ na^maa np’ioa .zrtwan rwaa mp^an ρ-ίΛ axnria ......r. Geodauer □innn Pi?

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