ADDRESSING DEVICE

Abstract: An addressing device has a supply wire (1), an addressing wire (9), an information wire (2) and a reference wire (3) that connect to a multitude of addressable units (28). The address wire is connected to voltage references (16) of low output impedance (17). If a current signal is drawn through the address wire (9), the current originates from the addressable unit that is located next to the control unit (26) that has not yet been addressed. This current signal is used to address the unit. Once this addressing cycle is accomplished, the addressable unit (28) disconnects, and the following addressing action is received by the next addressable unit.

Description: A D D R E S S I N G D E V I C E The invention relates to an addressing device as described in the preamble of claim 1 . The Swiss Patent 2846/88-6 proposes an addressing device that relies on the cable impedance to address a sequence of addressable uni ts, which is accomplished wi thout using any specially coded addresses, where all addressable uni ts are of the same kind, and where the addressing is performed by a standardized signal . This proposal consti tues a remakable progress compared to the prior state of the art, where addressing is performed by specially coded individual addresses at the si te of the addressabl e uni ts. Nevertheless, the proposed arrangement CH Pat. 2846/88-6 has the disadvantage that high frequencies have to be used in order to address the uni t, as the cable impedance is too low to sufficiently change the parameter of the standardized signal . On the one side, high frequencies imply a high power consumption of the used electronic components, they make them more expensive to produce, and on the other side, they imply high radio emissions of the used frequencies. This may make i t necessary to shield the complete cable, proposed in CH Pat. 2846/88-6, in order to be compatible wi th the local radio emission prescriptions, which may considerably raise production costs. One more disadvantage of the arrangement proposed in CH Pat. 2846/88-6 is the possibili ty to collectively address two nearby cells by the standardized signal, which is only insufficiently weakened between them. One may prevent that failure by using a higher addressing frequency, but this goes at the expense of the previously mentioned problems I concerning the emi tted power, the component cost and their power consumption . Finally, one further disadvantage of an arrangement following the proposal in CH Pat. 2846/88-6 is, that the impedance member, intended to weaken the standardized signal, has to be realized in the form of a capaci tor, which is an electronic component that cannot be integrated on a chip. */* It is the objective of the present invention to overcome the above mentioned disadvantages. This is accomplished as set forth in claim 1 The invention is based on the insight that i t is important for the addressing arrangement, to dispose of an impedance member that is of low value compared to the longitudinal cable impedance. The only way to accomplish this, while using conventional electronic devices, is an active impedance member. This impedance member is realized in the form of the output impedance 17 of a voltage reference 16 at the site of all cells. As they are electronically regulated voltage sources, that do not apreciably change under the load of varying currents, they have very low impedance values, which renders the addressing of the cells possible, even if the wire impedance 1 1 of the address wire is comparatively low. Claim 2 proposes measures intended to realize such an addressing arrangement using real components. Voltage references have certain tolerances originating from their fabrication process and their operating conditions, for example at different temperatures, that may only be reduced at a certain cost. The electronic regulation of the output value of an addressable uni t, that is connected to the address wire, which follows the vol tage reference input, which may be ei ther locally generated, or transmi tted through the reference wire, is done wi th an error term, the so-called offset vol tage, which is in general strongly temperature- dependent, and which adds to, or substracts from the vol tage to be regula ted. In applying the means set forth in claim 3 i t is guaranteed, that the vol tage drop across the cable impedance 4 of the reference wire between two succeeding addressable uni ts 28 has the effect, that the following addressable uni t produces a vol tage at i ts addressing output, that is lower by this vol tage drop. Following this reasoning, the vol tage drop across the cable impedance must be higher than the offset vol tage of the voltage reference 16 of the concerned addressable uni t in the worst case. The measures set forth in claim 4 guarantee that this voltage drop between two succeeding addressable uni ts has always the same value, and is independent of the distance between the control uni t and the addressable uni t. Even if the correct choice of the respective impedances has been made as set forth in claim 4, the drop of the reference voltage between two succeeding addressable units may vary slightly. This will specially occur in cases where a great number of addressable uni ts are attached to a long cable, and the sum of the longi tudinal impedances 4 of the reference wire provoke a voltage difference across the reference wire that cannot be neglected, and the voltage drop between two neighbouring cells may decrease. The measures set forth in claim 5 compensate this effect. The measures set forth in claim 6 provide that more than only one information source or information sink 12 per addressable uni t may be addressed. The measures set forth in claims 7 and 8 limi t the valid range of the addressing signal current in order to suppress electromagnetic interference signals. The measures set forth in claim 9 provide that the address wire and the information wire may be combined in cases where information output is concerned. The measures set forth in claim 10 propose a simple realization of the swi tches that are necessary for the addressing to take place. Claim 11 describes an addressable unit for the addressing arrange en t . Claim 12 describes a simple control uni t for the addressing arrangemen t . Further details of the invention will be explained following the execution examples of the drawings. They show: Ficr. 1 an overwiev of an arrangement as proposed by the invention, Ficr. 2 a preferred execution example of a cell, that works without a reference wire and where four different input or output operations may be performed by the addressable unit, Ficr. 3 a preferred execution example of a cell wi th measures intended to supress electromagnetic interference signals, Ficr. 4 an example of an addressable uni t using electronic circui try. */* Fig. 1 shows a typical execution example of an arrangement, that is proposed by the invention . As shown, the SUBSTITUTE SHEET arrangement comprises 5 wires mutually connecting the addressable uni ts 28 Z1 , Z2 to Zn to the control uni t 26. One of them is the supply wire 1 which is connected to a supply uni t 10 tha t provides appropria te vol tage between the supply inputs and the ground wire 23 for all cells. The information wire 2 connects all the local information sources or information sinks 12 via the information swi tch 14 to a centralized information input/ output uni t 13, that determines the direction and kind of information flow. The addressing is performed as follows: As soon as the addressing swi tch 21 of the control uni t 26 is closed, a corresponding current will be drawn through the address wire 9 and the limi ting resistor 22. As the output impedance 17 of the vol tage reference 16 of the first addressable uni t is considerably lower than the longi tudinal impedance of the address wire 11 that is located between the first addressable uni t Z1 next to the control uni t and i ts successor Z2, this current will be drawn out of the vol tage reference 16 of this first adressable uni t Zl . The relation between the output impedances 17 of the vol tage references 16 and the longi tudinal impedance of the address wire makes sure, that only the first cell Zl will be addressed and not the second. Of course, the longi tudinal impedances 4 and 1 1 of the respective address and reference wires are not necessarily electronic components. One will prefer to use a cable, the wire impedance of which corresponds to this impedance values. For such a cable one has to interprete the impedances 4 and 1 1 of all figures as equivalent values for the longi tudinal impedance of the cosidered wire. The same is valid for the symbols, standing for the output impedance 1 7 of the reference vol tages 16 of the figures, which are not real impedances. The symbol stands for the equivalent value of their output impedance, and i t is drawn SUBSTITUTESHEET G for clari ty purposes in the context of the addressing principle. At the si te of the addressed cell Zl , the addressing current is measured by the current detector 18, which may be a resistor, and the corresponding signal is fed to a threshold detector 19. Preferentially, this threshold detector 19 will be a schmi tt - trigger wi th hysteresis. As soon as a predetermined upper threshold is overridden i t changes state, closes the information swi tch 14, and connects the information source or -sink 12 wi th the information input and /or output device 13. Now information, in whatever direction, may be transmi tted. As soon as the transmission is terminated, the addressing switch 21 opens, no more cur en t flows through the address wire and the current detector 18, and the threshold detector 19 resets, opening the information switch 14 and the flip flop 20 changes state. This flip flop disconnects the cell Zl from the address wire 9 by opening the swi tch 15 and from the reference wire 3 by opening the swi tch 7. The cell will remain in this state until the supply vol tage will be shut down, and eventually brought up again, which will reset the flip flop to i ts starting posi tion, where the address switch 15 and the reference swi tch 7 are closed, and the information swi tch 14 is open . This addressing cycle for a cell is repeated, and the next cell Z2 is addressed, as the first one is disconnected . This second cell Z2 will finally disconnect from the wires 2, 3, and 9 when i ts addressing cycle is over, and the addressing cycle will repeat until the last cell Zn of the cable is addressed. Eventually the whole system is reset to i ts starting posi tion by shutting down the supply voltage and bringing i t up again . The reset member, necessary to accomplish this, has not been drawn in the figure. It is evident, that the reset function may be accomplished by a dedicated reset wire, or by a special state of the reference wire. The vol tage present at the input of the controllable voltage reference 16 is the resul t of the longi tudinal impedance of the reference wire 4, the transversal reference impedance 5, and of i ts termina ting impedance 6. By proper choice of this termina ting impedance 6, one may obtain a total impedance, composed of all longi tudinal and transversal impedances of the arrangement, that is constant and does not depend on the si te of the addressed unit. This proper choice of the values of the terminating impedance 6 and of the transversal impedances 5 of the reference wire, as mentioned above, which is a well-known technique, guarantee, that the current, that drains through the reference wire towards the not yet addressed rest of the cable, is constant, provided that all addressable units that have already been addressed, did open the reference swi tch 7. This implies that the voltage difference between two reference inputs of succeeding addressable units is always of the same value and does not depend on the address of the addressable uni t . One may use this vol tage difference in order to compensate for tolerances, imprecisions and temperature dependencies of the reference voltages 16 of the individual addressable units, that one has to account for in real cases. As this vol tage difference is only a function of the current that flows through the reference wire and of i ts longitudinal impedance 4, i t may be of almost any value. If one supposes that the cable properties and the properties of the addressable uni t are determined, this vol tage difference is only a function of the cable terminating SUBSTITUTE SHEET ? impedance. By proper choice, a compromise between the power consumption and the production cost, or the cost to adjust the pecision of the addressable uni ts of an arrangement as set forth by the invention, is achievable. */* Fig. 2 shows an addressable uni t 28 attached to the information wire 2, the address wire 9 and to the supply- and the ground wires 1 and 23. This is a variant of the invention using four wires and no reference wire. As already mentioned, this may be accomplished by either using a very precise reference vol tage 25, by chosing a sufficiently high value for the longitudinal impedance 11 of the address wire, or by chosing a very low value for the output impedance 17 of the local reference voltages 16 or by any combination of this measures. The local reference voltage 25 is present in every addressable unit and i ts value controls the voltage reference 16. The precision of this local reference voltage must be sufficiently high, so that no intolerable values of voltage differences at the output of the addressable uni ts create a current through the address wire, which, in turn, may be detected by the current detector 18 of a neighbouring cell . It is left to a cost trade-off to decide wether it is advantageous to realize such a precise local voltage reference 25 at the site of all addressable units (Fig. 2), or to transmi t a common reference vol tage to all addressable uni ts by a special reference wire (Fig. 1 ) . The example in Fig. 2 illustrates the control of more than one information soure or -sink 12 at the site of the addressable uni t 28. This may be specially advantageous if one desires to send and receive information, the location SUBSTJTUTE SHEET of which is the same. As an example one could consider the measurement of the local tempera ture and the control of extinction valves for fire protection at the same si te by a single addressable uni t . The addressing of the informa tion sources or information sinks 12a . . 12d of fig. 2 is accomplished in a sequential manner. At the moment when the power supply comes up, a reset member 27 generates a defined state of the shift register, tha t is composed of the cells 20a to 20 f. This state is characterized by all cells 20b to 20 f being set to logical zero, and the cell 20a to logical one. The shift register cells control the information switches 7a to 7d of the respective information sources or information sinks 12a to 12d. If their output is logical one, the swi tches 7a to 7d are closed, otherwise they are open. The shift register cell 20f is connected to the address swi tch 15 of the cell 28, and an output of logical zero closes, one of logical one opens the swi tch . At every instant where the threshold detector 19 changes state, the contents of the shift register, composed of the cells 20a to 20 f are shifted right by one place. At the first detection of the threshold detector the switch 7a is closed, and information is transmi tted, at the second detection the swi tch 7b is closed, and so forth until the last information swi tch 7d is closed. At the instant of the next detection of the threshold detector the shift register 20a to 20 f will shift i ts contents once more to the right by one place, and this will open all swi tches of the addressable uni t, including the address swi tch 15. In consequence, the following addressing cycle will be recei ved by the next addressable uni t 28 tha t succeeds the one tha t has just been addressed. Λ O An addressable uni t in this sta te maintains the power supply only for the shift register, and all other power consuming circui try is disconnected . At the instan t when the next reset and power up occurs, the reset member 27 will crea te the above mentioned ini tal state. One may, of course continue the cascaded alignment of shift register cells 20a to 20 f indefini tely in order to concentrate a grea t number of inputs and/or outputs at the si te of the addressable uni t . */* Figure 3 shows an addressable uni t 28 of a five wire version of the present invention . This is a version comprising the supply wire 1 , the ground wire 23, an address wire 9 and a combined reset- and reference wire 30, where this wire 30 transmi ts a common reference voltage, that is generated in the control uni t 26, to all addressable uni ts, in a similar manner as in fig. 1. The impedances 4, 5, and 6 lower the reference voltage signal as already explained (Fig. 1 ) . The example in fig. 3 shows the supression of interference signals. It is of great importance for real systems, that are exposed to electromagnetic interference, that the addressing technique, that is performed by the transmission of a current signal works satisfactorily . One has to guarantee, that currents, that are induced in the address wire will not inadvertently trigger the address of one or more cells. Besides the usual measures for electriclal interference supression, that are normally provided, as the shielding of SUBSTITUTESHEET A A the cable and/or the use of twisted wire pairs for sensible signals wi ti their own ground wire, provision is made for two further measures, tha t are explained following the execution example of fig. 3. The first measure is the execu tion of the threshold detector 19 in the form of a window detector 24. It will issue an output si gnal if and only if the input vol tage, tha t is taken from the curren t detector 18 has been found between a minimal and a maximal permissible value during a certain time . This function is explained in the figures 3a, 3b and 3c, where three differen t input signal forms are drawn . The signal of fig. 3a shows an insufficien t signal *or the trespassing of the detector. The signal 's ampli tude is always below the minimal permissible value 37. The detector will, in con trast, issue an output signal in the case of the signal drawn in fig. 3b as soon as the input signal falls below the minimal permissible value 37, while the input signal form drawn in figure 3c will not yield a detection signal as the maximal permissible value has been trespassed. This permi ts the elimina tion of less important interference signals, the ampli tude of which falls below the minimal permissible value 37, and of more importan t interference signals that override the maximal permissible value 36, from the addressing current signal . At the si te of the control uni t, provision is made by the current limi ting resistor 22 that the curren t, tha t flows in the state, where the addressing swi tch 21 is closed, corresponds approxima tely to the mean val ue between the minimal and the maximal permissible val ues 37 and 36. No further expli ca tion is gi ven for the electronic circui try, tha t is necessary to realize the window detector, as i t is composed of a combina tion of standard SUB S TITUTESHEET electronic components, using schmi tt triggers, logic gates and flip - flops to obtain the wanted function . One may memorize the trespassing of the maximal permissible value 36 in a flip flop, the logic state of which is read at the negative going edge of the input signal through the threshold that is defined by the minimal permissible value 37. If at that moment the flip- flop is set, no output signal is issued. In the other case, the minimal permissible value 37 has been trespassed and not the maximal permissible value 36, and a one - shot will issue an output signal . The second measure for interference supression comprises a shift register made of the cells 20a to 20f. This shift register is loaded by a reset member 27, where, as already mentioned, the first cell 20a is loaded wi th logical one, and all others with logical zero. The reset member will load the shift register if there is a corresponding signal at its input. This input of the reset member is connected via an or gate 31 to the combined reference- and reset wire 30. If the reference vol tage a t i ts input falls below the threshold of the or gate 31 , i t will issue a corresponding signal to the reset member 27, and the shift register 20a to 20 f will be set to i ts ini tial state. The addressing cycle for the addressable uni t 28 goes on as follows: Every time the window detector 24 issues a signal, the contents of the shift register are shifted right one place. After the fourth output signal of the window detector the cell 20e of the shift register changes state and the swi tch 14 is closed for information transmission . At the same time the cell 20e of the shift register issues an inhibi t signal to the reset member 27 preventing i t to abort an ongoing information transmission by a reset signal to the shift register. 3 The next following pulse issued by the window detector 24 will shift the contents of the shift register right by one place, and the swi tches 14 and 15 are opened. If, by interference in the address wire, the window detector issues an output signal, the contents of the the shift register will be shifted right one place for every such event . The timer, the output of which is connected to one of the inputs of the or gate 29 will regularily reset the shift register 20a to 20f by the reset member 27. As a coseguence, i t is necessary, in order to successfully address the addressable uni t 28, tha t at least four pulses are issued by the window detector 24 before the timer 29 resets the entire shift register. Of course i t is possible, to insert any number of shift register cells between the cell 20e, that starts the addressing action and the cell 20f that terminates it. This is not shown in fig. 3. The resul t would be, that one needs a certain number, say four pulses of the window detector 38, to terminate the addressing, and the addressing securi ty will be higher while information is transmi tted. This technique will be specially advantageous if the information transmission takes a long time. In this case, the reset member 27 will have to be modyfied so that i t cannot issue a reset signal, tha t is caused by interference signals, while the information transmission is still ongoing. */* The example drawn in fig. 4 shows the electronic circuitry of the reference vol tage 16 of an addressable uni t 28 in detail . Only the input stage of the addressable uni t and SUBSTITUTE SHEET y its interface to the supply wire 101, the reference wire 103, the address wire 109 and the ground wire 123 is shown, and the details of the rest 32 of the addressable uni t are not drawn . The reference vol tage 16 comprises a transistor 33 and an operational amply fier 35, that, together wi th a biasing resistor 34, are connected in such a manner, that the reference - output 109, attached to the address wire 9, is at the same vol tage level as the reference input 103, attached to the reference wire 3. The reference input 103, that is attached to the reference wire 3 is connected to the transversal reference impedance 5. The output voltage of the reference voltage 16 is regulated in a feedback-loop and i t is independent of the output current that is drawn through the address wire. Consequently, the output impedance of the reference voltage 16 will be very low. As current is drawn out of the reference voltage 16, the voltage at i ts output pin 109 will not change apreciably, but the vol tage across the current detector, which is a resistor in the example, will change in proportion to the current in the address wire 9. If the voltage across the current detector 18 becomes greater than a predetermined value, the other parts 32 of the addressable uni t 28 will work as provided, and eventually, when the transmission is over, they will provide the signals to open the swi tches 15a, 15b and 7. The swi tches are transistors in the example, that change to a state of high impedance between the collector and emi tter pins, as the base vol tage is lower than i ts threshold. The swi tch 15 in the example of fig. 4 is doubled, and one part 15a of i t disconnects the biasing resistor 34 from the ground wire, and the other part 15b closes the transistor SUBSTITUTE SHEET 33 by shorting i ts base to the ground wire . The transistor 33 has two functions, namely once as vol tage regulator, and, if i ts base is grounded by the secondary transistor 15b, as swi tching element . The transistors 15a and 7 commute at base signals of zero vol ts, but the transistor 15b a t a posi ti ve vol tage, and the circui try 32 in fig. has two complementary outputs that issue the same signal once wi th posi tive and once wi th inverted polari ty to the respecti ve transistors. Of course i t is possible, to invert the circui try in the sense, that the addressing current flows into the addressable uni t 28, where i t is measured by a resistor that is connected to ground, and where this current signal is interpreted as an addressing signal . In thi. τ,ase, all NPN - transistors have to be replaced by their _.* ? counterparts, and the circui t will work in an equivalts.'t manner as in fig. 4, where all polari ties and the current flow direction are inverted. Of course, in this case, the resistor 22 has to be tied to a posi tive voltage instead to ground. Furthermore i t is possible, and i t will be the preferred choice in a heavily disturbed environment, to provide two address wires, one of them sourcing current to, and the other sinking current out of the addressable uni t. In this case, the address detector is modyfied so that the two address currents have to be measured at the same time in order to validate the address . As, in general, interfering induced currents in the address wire have the same direction, this method consti tutes a very efficient way to supress interference signals. */*

Claims: Ab I C L A I M 1. Addressing arrangement comprising a cable with at least an address generator (22) connected to an address wire (9), at least one information wire (2) and at least one supply wire (1), that connects a multitude of addressable units (28) with attached detectors (18), where all addressing switches (15) are closed in their initial state and all information switches (14) are open in their initial state, where the information switch (14) of the addressed addressable unit (28) is closed, and the information switches of all other addressable units in the arrangement are open, where information is transmitted between a central information input/output means (13) and an information source or -sink at the site of the addressable unit, and where after transmission of the information of an addressable unit the address switch (15) and the information switch (14) are opened, wherein: voltage references (16) of low ouput impedance (17) are connected to the address wire (9) by the address switch (15), wherein a current signal is sent through the address wire in order to address the addressable unit (28) that is located next to the control unit (26), and that has not yet beeen addressed, wherein this current signal originates from or flows into the addressable unit (28) that has not yet been addressed, and that is located next to the control unit (26), as the output impedance (17) of the reference voltage (16) is low compared to the longitudinal impedance (11) of the address wire, and wherein this current signal is measured at the site of the addressable unit by a detector (18) and is interpretable as an addressing signal . SUBSTITUTESHEET 2. Addressing arrangement as set forth in claim 1 , wherein the vol tage references ( 16) are ger.erated by a centralized reference vol tage (8) of the arrangement in the control uni t, and where this reference value is transmi tted by a reference wire (3) to all addressable uni ts. 3. Addressing arrangement as set forth in one of the claims 1 and 2, wherein the refreence wire (3) has a longi tudinal impedance (4) , a transversal impedance (5) and a terminating impedance (6) , whose proportion assures, that the total impedance of the reference wire from the addressed uni t toward the termina ting impedance has always the same value, and is independent of the location where the addressable uni t is attached to the cable. 4. Addressing arrangement as set forth in one of the claims 1 to 3, wherein the transversal impedances (5) of the reference wire that belong to addressable uni ts (28) that are already addressed, are disconnect able from the reference wire. 5. Addressing arrangement as set forth in one of the claims 1 to 4, wherein the reference vol tage (8) of the control uni t (26) is made in such a manner, that the reference vol tage that is output to the reference wire is regulated corresponding to the current drawn, and where the reference voltage drop between the addressed uni t and the next addressable uni t is constant, and does not depend on the si te of the addressable uni t . 6. Addressing arrangement as set forth in one of the claims 1 to 5, wherein by a first addressing action a first information source or -sink ( 12a) is connected to the centralized information input/output uni t ( 13) , that by a second addressing action a second information source or - sink ( 12b), and so forth, until by a last addressing action the addressing of the addressable uni t (28) is terminated. 7. Addressing arrangement as set forth in one of the claims 1 to 6, wherein the condi tion, that the addressing current flowing through the addressing wire is interpreted as signal to start or terminate the addressing of the addressable uni t, is, tha t a certain number of detections have to occur during a time, that is determined by a timer (29) . 8. Addressing arrangemen t as set forth in one of the claims 1 to 7, wherein the detection of the addressing current takes place if and only if the value of the current is higher als a predetermined minimal value (37) and lower than a predetermined maximal value (36) . 9. Addressing arrangement as set forth in one of the claims 1 to 8, wherein the addressing current comprises a fraction that determines the addressing of the addressable unit (28) and another fraction, the value of which is interpretable as information that is transmi tted to the addressable unit by the control uni t (26) , combining the functions of the address wire and of the information wire in a common wire. 10. Addressing arrangement as set forth in one of the claims 1 to 9, wherein the reference voltage ( 16) and the address swi tch ( 15) are made out of one and the same transistor (33) . 11. Addressable uni t to realize an arrangement as set forth in one of the claims 1 to 10, comprising a reference vol tage ( 16) of low output impedance (17) connectable to the address wire, a current detector ( 18) and a threshold detector ( 19) for the signal issued by this current detector, an address swi tch ( 15) and an information swi tch ( 14), where the switches ( 14) and ( 15) are controllable by a flip - flop (20) , that is controlled by the threshold detector ( 19) , where the address swi tch ( 15) connects the reference vol tage ( 16) to the address wire (9) , and where the information switch (14) connects the information wire (2) to an information sink or -source (12). 12. Control unit (26) for an addressing arrangement as set forth in one of the claims 1 to 10 comprising a supply unit (10) providing an appropriate voltage supply between the supply wire (1) and the ground wire (23) an information input and /or output unit (13) able to send or receive information through the information wire (2) a current source or current sink (22), that is connected to the address wire by a switching element (21), where a specially adapted electronic circuit establishes the correspondence between the number of the controlling pulses issued to the switch (21) and the address of the addressabl e unit. */*

Inventors: VOCKENHUBER PETER, VOCKENHUBER, PETER
Applicants: VOCKENHUBER PETER, VOCKENHUBER, PETER
Application year: 1991
Main classification: H04Q9
IPC codes: G06F13, H04Q9