GB2271255A - Method of transmitting data from a plurality of data transmitters on a common data line - Google Patents
Method of transmitting data from a plurality of data transmitters on a common data line Download PDFInfo
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- GB2271255A GB2271255A GB9319060A GB9319060A GB2271255A GB 2271255 A GB2271255 A GB 2271255A GB 9319060 A GB9319060 A GB 9319060A GB 9319060 A GB9319060 A GB 9319060A GB 2271255 A GB2271255 A GB 2271255A
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- G—PHYSICS
- G08—SIGNALLING
- G08C—TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS
- G08C15/00—Arrangements characterised by the use of multiplexing for the transmission of a plurality of signals over a common path
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J7/00—Multiplex systems in which the amplitudes or durations of the signals in individual channels are characteristic of those channels
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Abstract
The invention relates to a method of transmitting data of a plurality of data transmitters (S1, S2 ..., Sn) on a common data line 701, and a device for carrying out the method, in which method binary signals in the form of positive and negative signal level changes are transmitted by the data transmitters (S1, S2 ..., Sn) onto the data line 701 and signal level changes occurring on the data line are sensed and the frequency and the pulse duty ratio of each data transmitter are derived from the time intervals of the positive and negative signal level changes. In a design variant, the frequency characterizes the data transmitter and the pulse duty ratio characterizes the information to be transmitted of the data transmitter and, in another design variant, the pulse duty ratio characterizes the data transmitter and the frequency characterizes the information to be transmitted of the data transmitter. <IMAGE>
Description
2271255 Method of transmitting data from a plurality of data transmitters
on a common data line The invention relates to a method of transmitting data from a plurality of data transmitters on a common data line to a central receiving unit, and a device for carrying out the method, in which method the data transmitters are in each case capable of two logical output states and the emission of pulse-width-modulated digital signals and are adapted in each case to be connected via a first resistor to the data line and data signals transmitted to the central receiving unit can be picked off there at a resistor at least contributing to termination of the data line.
A method by which the data are digitally conditioned is already known. The information transmitted on the data line is in this case subdivided into a first part, which characterizes the respective data transmitter, and a second part, which characterizes the corresponding data of the respective data transmitter. The corresponding device is in this case designed in such a way that the data from the data transmitter have to be digitized. The data transmitter can bring the information onto the data line at any time. This method and the device are known as a data bus, for example for the transmission of data between a plurality of computers.
Furthermore, it is known to connect an analogue/digital converter (A/D converter) in series before a computer. Then, by means of a series resistor, individual sensors are connected to this A/D converter via a common line, the analogue signals of which are digitized by the A/D converters and can consequently be processed by the computer.
The present invention seeks to design a method of transmitting data from a plurality of data transmitters on a common data line and a device for carrying out the method in such a way as to obtain as simple a structural form as 2 possible with regard to the components required for carrying out the method and for designing the device.
According to one aspect of the present invention there is provided a method of transmitting data of a plurality of data transmitters on a common data line to a central receiving unit, in which method the data transmitters are in each case capable of two logical output states and the emission of pulse-width-modulated digital signals and are adapted in each case to be connected via a first resistor to the data line and data signals transmitted to the central receiving unit can be picked off there at a resistor at least contributing to termination of the data line, wherein - digital signals in the form of positive and negative signal level changes are transmitted by the data transmitters via corresponding first resistors simultaneously onto the data line, - jump-like signal level changes occurring in the quasianalogue sum signal resulting in this respect on the data line are sensed by the central receiving unit, - in the central receiving unit the current frequency and the current pulse duty ratio of the digital signal of each of the data transmitters are derived or recovered from the time intervals of past positive and negative signal level changes, and - the frequency in each case characterizes the data transmitter and the pulse duty ratio in each case characterizes the data value currently to be transmitted of the data transmitter concerned.
According to a second aspect of the invention there is provided a method of transmitting data by a plurality of data transmitters on a common data line to a central receiving unit, in which method the data transmitters are in each case capable of two logical output states and the emission of pulse-width-modulated digital signals and are adapted in each case to be connected via a first resistor to the data line and data signals transmitted to the central 3 receiving unit can be picked of f there at a resistor at least contributing to termination of the data line, wherein digital signals in the f orm of positive and negative signal level changes are 'transmitted by the data transmitters via corresponding first resistors simultaneously onto the data line, - jump-like signal level changes occurring in the quasianalogue sum signal resulting in this respect on the data line are sensed by the central receiving unit, - in the central receiving unit the current frequency and the current pulse duty ratio of the digital signal of each of the data transmitters are derived or recovered from the time intervals of past positive and negative signal level changes, and - the pulse duty ratio in each case characterizes the data transmitter and the frequency in each case characterizes the data value currently to be transmitted of the data transmitter concerned.
The invention also provides a device for carrying out the methods wherein - each data transmitter comprises a switchable isolating means, - by means of said isolating means the data line from each data transmitter is switchable with equal priority and at any time via the first resistor assigned to each data transmitter, to a reference potential, and - the central receiving unit comprises an A/D converter for converting the quasi-analogue sum signal obtained from the data line into a digital signal which can be evaluated digitally for positive and negative signal transitions.
Advantages of the invention over the known prior art are that a simplification is obtained with regard to the required components while maintaining adequate reliability in the transmission of the data.
The method according to the invention is based on the fact that preferably a plurality of data transmitters are connected to a data line for transmitting the data. In 4 this case, the signals transmitted by the data transmitters onto the data line assume binary values. In the transmission of data of a data transmitter, the frequency and the pulse duty ratio are evaluated. Consequently, a plurality of data transmitters can transmit data on one data line. since the evaluation'of one of the two variables (frequency or pulse duty ratio) can be used to detect from which data transmitter a transmission has come and the evaluation of the other variable (pulse duty ratio or frequency) can be used to obtain the transmitted data (information).
An exemplary embodiment of the invention is described in more detail below and is represented diagrammatically in the drawing, in which:
Fig. 1 shows a representation concerning the changes of signal levels of a plurality of data transmitters connected to one data line on the time axis, Fig. 2 shows the variation over time of the signal on the data line, in the case of the changes of the signal levels according to Fig. 1, Fig. 3 shows a f irst f low chart of the method, in which the pulse duty ratio characterizes the data transmitter and the frequency characterizes the data to be transmitted, Fig. 4 shows a second f low chart, in which the frequency characterizes the data transmitter and the pulse duty ratio characterizes the data to be transmitted, Fig. 5 shows a third flow chart, in which the pulse duty ratio characterizes the data transmitter and the frequency characterizes the data to be transmitted, Fig. 6 shows a fourth f low chart, in which the frequency characterizes the data transmitter and the pulse duty ratio characterizes the data to be transmitted and Fig. 7 shows a device for carrying out the method.
As evident from Fig. 1, changes of the signal level are transmitted by the data transmitters onto the data line. These changes of the signal level are then evaluated in order to determine the frequency and the pulse duty ratio of the individual data transmitters. In the exemplary embodiment represented, three data transmitters, denoted by S1, S2 and S3, are connected to a data line. The designation Sl+ then means that an active signal level change is transmitted by the data transmitter S1 onto the data line. Correspondingly, the designation Si- means that a signal corresponding to a reverse signal level change (reversed with respect to the "active" change) is transmitted by the data transmitter S1 onto the data line. The meaning of the designation of the other data transmitters (S2+, S2-, S3+, S3-) is then obtained correspondingly. Furthermore, Fig. 1 reveals that each level change is assigned precisely one point in time. In the data receiver, the voltage level is then evaluated to the effect that the jumps are detected and that these jumps are assigned the respective points in time (t0P t1P t2r t3f t40 t51 t6, t7, tS, tg and tjo). Since the data transmitters transmit in an unsynchronized manner onto the data line, it may happen that a double signal level change of the same direction occurs at a particular time. In this case, this signal level change is assigned two points in tine. On the basis of these data, the frequencies and pulse duty ratios of the individual data transmitters can then be detected - as described below. In the exemplary embodiment represented, the data transmitter S1 has a recurrence of 5 time units and a pulse duty ratio of 0. 2, the data transmitter S2 has a recurrence of 3 time units and pulse duty ratio of 0.33 and the data transmitter S3 has recurrbnce of 4 time units and a pulse duty ratio of 0.5. The recurrence in this case means the inverse of the frequency.
Fig. 2 reveals a representation of the signal obtained on the data line over time if the data transmitters S1, S2 and S3 are connected to the data line and the signal level changes take place in a way corresponding to the representation of Fig. 1.
Fig. 3 shows a f irst f low chart of the method, in which the pulse duty ratio characterizes the data trans- 6 mitter and the frequency characterizes the data -to be transmitted. As described in the case of Fig. 1, the times of the positive and negative jumps are recorded.
In the case of the flow chart shown in Fig. 3, the method of evaluating the signal level changes is described, this method being carried out immediately after establishing the negative signal level change at the point in time t.. Then all the past points in time of signal level changes which lie in a time interval which corresponds to the maximum possible recurrence of the three data transmitters are taken into consideration for the evaluation. The maximum possible recurrence in this case refers to the time interval which corresponds to the minimum possible frequency.
The flow chart shown can be run through cyclically. For evaluation, past points in time which lie within the said time interval are required. Therefore, in the step 301 it is first of all checked whether points in time lying further back in the past, considered from the current time, than the said time interval are stored. If it is established in this check that such points in time are stored, in the step 302 these points in time are then erased in a manner corresponding to a stack memory which operates on the FIFO principle.
In the step 304, the current time is then stored as the point in time if a signal level change has been established in the step 303. Apart from the point in time, in this case the direction of the signal level change is also stoked.
In the step 305, an evaluation of these measurement data then takes place by initially determining each possible recurrence.
The description of the present exemplary embodiment in this case relates to the current time in such a way that in the step 304 the point in time tg was assigned a negative signal level change. Since a negative signal level change was established at the point in time tg, in the step 305 the time interval between the point in time t. and each point in
7 time (to, t2r t51 t6) in the said time interval at which a negative signal level change was likewise established is calculated. Consequently, the following time intervals are calculated tabst,wl t9 - t6 = 1.5, tabst,w2 tg - t5 = 2.7, tabst,W3 t9 - t2 = 4.5, tabst,w4 tg - to = 5.0.
In the step 306, each possible pulse duty ratio is then calculated. In this case, each point in time lying in the time interval which was assigned a positive signal level change (tl 1 t31 t4 t t71 tS) is evaluated with each of the time intervals calculated in the step 305 with regard to the pulse duty ratio. only the pulse duty ratios for which it is true that the point in time of the positive signal level change (tl, t31 t41 t7, t.) lies after the point in time of the earlier negative signal level change (tot t21 t51 t6) being calculated. Thus, the following pulse duty ratios are calculated. the figures in the last column concerning the values of the present exemplary embodiment:
ttastll 1 - (tl - t9Mtabst,w4 = 0.06j. ttast21 = 1 - (t3 - tg)/tabst,w4 = 02# ttast22 = 1 - (t3 - tg)/tabst,w3 = 0.11# ttast31 = 1 - (t4 tg)/tabst,w4 = 03p ttast32 1 - (t4 - tg)/tabst,w3 = 0.221 ttast41 1 - (t7 - t9Mtabst.w4 = 0.861 ttast42 1 - (t7 - tgMtabst,w3 = 0.8440 ttast43 1 (t7 - tg)/tabst,w2 = 0.741 t - (t7 - t tast44 1 9)/tabst,wl= 0.5330 ttast51 1 - (t8 - t9Mtabst,w4 = 0'91 ttast52 1 - (t8 - t9Mtabst,w3 = 0.889P ttast53 = 1 - (t8 - tgMtabst,w2 = 0.8131 ttast54 = 1 - (t8 -t9Mtabst,wl = 0.667.
8 In the step 307, the pulse duty ratios calculated in the step 306 are then compared with the pulse duty ratios of the data transmitters connected to the data line. If there is agreement, it can be concluded that the corresponding signals were sent by the data transmitter of which the pulse duty ratio coincides with the corresponding calculated pulse duty ratio. In the exemplary embodiment shown, these pulse duty ratios are, according to the. description of Fig. 1, equal to 0.2 or 0.33 or 0.5. If a certain tolerance range to compensate for measuring errors, which may be for example 0.01, is also taken around these values of the pulse duty ratio, it is shown that only the pulse duty ratio ttast21 satisfies the condition. This pulse duty ratio is in this case assigned to the data transmitter S1, which has a pulse duty ratio of 0.2. If a plurality of the calculated pulse duty ratios can be assigned to one data transmitter, it is not possible to state reliably from which data transmitter the signal originates. Similarly, it may happen that none of the pulse duty ratios lies within one of the described tolerance ranges. In this case, no reliable assignment to a data transmitter is possible. The enquiry in the step 307 is consequently such as to investigate whether precisely one of the calculated pulse duty ratios coincides. at least within a tolerance range, with one of the pulse duty ratios predetermined by the data transmitters. If this is the case, in the step 308 the frequency used in the calculation of this pulse duty ratio is evaluated in order to obtain the information of the corresponding data transmitter. otherwise, it is not possible to state reliably from which data transmitter the signal level change was transmitted. In a particularly advantageous embodiment,. however,, all the frequencies which were used as a basis for the calculation of the corresponding pulse duty ratios and come into consideration according to the result of the check in step 307 can be checked for their plausibility in a step 309. This plausibility check may in this case include checking the value range, obtained from the respective frequency. of the
9 data transmitter. Similarly, changes in comparison with the previous data values can be evaluated with respect to the individual data transmitters. If this plausibility check in the step 309 reveals that only one of the frequencies coming into consideration on the basis of the check in the step 307 can correspond to the information of a data transmitter. in the step 310 the frequency used in the calculation of the corresponding pulse duty ratio is evaluated in order to obtain the information of the corresponding data transmitter. Otherwise, no information of a data transmitter can be obtained in this programme cycle.
In principle, it is also possible according to the exemplary embodiment of Fig. 4 that the frequency characterizes the data transmitter and the pulse duty ratio characterizes the data to be transmitted.
In the case of the flow chart shown in Fig. 4, the method of evaluating the signal level changes is described, this method being carried out immediately after establishing the negative signal level change at the point in time t9. Then all the past points in time of signal level changes which lie in a time interval which corresponds to the maximum possible recurrence of the three data transmitters are taken into consideration for the evaluation. The maximum possible recurrence in this case refers to the time interval which corresponds to the minimum possible frequency.
The flow chart shown is run through cyclically. For evaluation, past points in time which lie within the said time interval are required. Therefore, in the step 401 it is first of all checked whether points in time lying further back in the past. considered from the current time, than the said time interval are stored. If it is established in this check that such points in time are stored. in the step 402 these points in time are then erased in a manner corresponding to a stack memory which operates on the FIFO principle.
In the step 404, the current time is then stored as the point in time if a signal level change has been established in the step 403. Apart from the point in time, in this case the direction of the signal level change is also stored.
In the step 405, an evaluation of these measurement data then takes place by initially determining each possible recurrence.
The description of the priesent exemplary embodiment in this case relates to the current time in such a way that in the step 404 the point in time t9 was assigned a negative signal level change. Since a negative signal level change was established at the point in time tg, in the step 405 the time interval between the point in time tq and each point in time (tot t2Y t5P t6) in the said time interval at which a negative signal level change was likewise established is calculated. Consequently, the following time intervals are calculated t 1.5, abst,wl t9 - t6 tabst,w2 t9 - t5 = 2.7, tabst,w3 t9 - t2 = 4.5, tabst,w4 t9 - to = 5.0.
In the step 406, the calculated time intervals are compared with the recurrences possible on the basis of the data transmitters used. In the present exemplary embodiment, these values are equal to 3 or 4 or 5. If in this case one or more of the calculated time intervals lie within a certain - tolerance range around possible values for the recurrence, in the step 407 the possible pulse duty ratios are calculated. Otherwise, the signal level change could not be assigned to a data transmitter. The current run through of the flow chart of Fig. 4 is then aborted. If the tolerance range is assumed to be, for example, 0.01, it is shown that only the time interval tabst,w4 comes into consideration as a possible recurrence of a data transmitter.
In the step 407, all possible pulse duty ratios for 11 the recurrences which come into consideration according to the check in the step 406 are calculated, here again, in analogy with the description of the step 306, only the pulse duty ratios for which it is true that the point in time of the positive signal level change lies after the point in time of the earlier negative signal level change are calculated. Thus, the following pulse duty ratios are calculated, the figures in the last column concerning the values of the present exemplary embodiment:
ttastil 1 - (ti - tg)/tabs't,w4 = 0.06r ttast21 1 - (t3 - t9Mtabst,w4 = 0-2, t (t 't tast31 1 4 9)/tabst,w4 = 0-3, ttast41 1 (t7 t9Mtabst,w4 0.861 ttast51 1 (t8 t9Mtabst,w4 0-9- In the check corresponding to the step 408, the pulse duty ratio which is assigned to this data transmitter is then selected. It emerges from the value of the recurrence tabst,w4 that the transmitter concerned is the data transmitter S1. which transmits with a pulse duty ratio of 0. 2. This pulse duty ratio is in this case subject to certain variations in order to be able to transmit the information of the data transmitter. If, for example, 0.06 is assumed for the possible range of the variations of the pulse duty ratio, it is shown that only the pulse duty ratio ttast21 comes into consideration.
If it emerges in the check in the step 408 that a plurality of pulse duty ratios come into consideration, it may further be attempted, for example, to establish definitively which is concerned from the changes of the respective data values with time.
corresponding to the step 308 (there with respect to the frequency), there then takes place in the step 409 an evaluation of this pulse duty ratio, in order to obtain the information of the corresponding data transmitter.
Fig. 5 reveals a further exemplary embodiment of a 12 sequence of the method according to the invention, in which the pulse duty ratio characterizes the data transmitter and the frequency characterizes the data to be transmitted.
In the case of the flow chart shown in Fig. 5, the method of evaluating the signal level changes is described, this method being carried out immediately after establishing the positive signal level change at the point in time t 10 Then all the past points in time of signal level changes which lie in a time interval which corresponds to the maximum possible recurrence plus the tine of the duration of the negative signal level of each of the three data transmitters are taken into consideration for the evaluation. The maximum possible recurrence in this case refers to the tine interval which corresponds to the minimum possible frequency.
The flow chart shown is run through cyclically. For evaluation, past points in time which lie within the said time interval are required. Therefore, in the step 501 it is first of all checked whether points in tine lying further back in the past, considered from the current tine, than the said time interval are stored. If it is established in this check that-such points in tine are stored, in the step 502 these points in tine are then erased in a manner corresponding to a stack memory which operates on the FIFO principle.
In the step 504, the current tine is then stored as the point in tine if a signal level change has been established in the-step 503. Apart from the point in time. in this case the direction of the signal level change is also stored.
In the step 505, an evaluation of these measurement data then takes place by initially determining each possible recurrence.
The description of the present exemplary embodiment in this case relates to the current time to the effect that in the step 505 the point in time tjo was assigned a positive signal level change. Since a positive signal level
13 change was established at the point in time tlo, in the step 505 each time interval is calculated from the number of points in time of negative signal level changes (to 1 t21 t51 t6) in the said time interval. Consequently, the following time intervals are calculated:
t abst,w11 t 9 - t6 = 1.5, t = 2.7, abst,w21 tg ts t abst,w31 t9 - t 2 = 4.5, tabst,w41 tg - to = 5.0.
tabst,w12 t6 - t5 = 1.2,, tabst,w22 t6 - t2 = 3.0, t abst,w32 t6 - t 0 = 3.5, tabst,w13 = t5 - t2 = 1.8, tabst,w23 = t5 - to = 2.3, tabst,w14 = t2 - to = 0.5.
In the step 506, the following pulse duty ratios are then calculated:
t tast,w11 = (t10 - t9) / tabst,w11 = 0,67JY ttast,w21 = (t10 - tg) / tabst,w21 = 037, ttast,w31 = (t10 - tg) / tabst,w31 = 0.221 ttast,w41 = (t10 - t9) / tabst,w41 = 02, ttast,w12 = (t10 - t,6) / tabst,w12 = 208P ttast,w22 = (t10 - t6) / tabst, w22 = 0.8301 ttast,w32 = (t10 - t6) / tabst,w32 = 0.7101 ttast,wi3 = (t10 - t5) / tabst,w13 = 2.03, ttast,w23 = (t10 - tS) / tabst,w23 1.59, ttast, w14 = (t10 - t2) / tabst,w14 11.
In the step 507. the pulse duty ratios calculated in the step 506 are then compared with the pulse duty ratios of the data transmitters connected to the data line. If there is agreement, it can be concluded that the corresponding signals were sent by the data transmitter of which the pulse duty ratio coincides with the corresponding calculated pulse 14 duty ratio. In the exemplary embodiment shown, these pulse duty ratios are, according to the description of Fig. 1, equal to 0.2 or 0.33 or 0.5.. If a certain tolerance range to compensate for measuring errors and changes in the data value, which may be for example 0.01, is also taken around these values of the pulse duty ratio, it is shown that only the pulse duty ratio ttastw41 satisfies the condition. This pulse duty ratio is in this case assigned to the data transmitter S1, which has a pulse duty ratio of 0. 2. If a plurality of the calculated pulse duty ratios can be assigned to one data transmitter, it is not possible to state reliably from which data transmitter the signal originates. Similarly, it may happen that none of the pulse duty ratios lies within one of the described tolerance ranges. In this case, no reliable assignment to a data transmitter is possible. The enquiry in the step 507 is consequently such as to investigate whether precisely one of the calculated pulse duty ratios coincides, at least within a tolerance range, with one of the pulse duty ratios predetermined by the data transmitters. If this is the case, in the step 508 the frequency used in the calculation of this pulse duty ratio is evaluated in order to obtain the information of the corresponding data transmitter. otherwise, it is not possible to state reliably from which data transmitter the si g-nal level change was transmitted. In a particularly advantageous embodiment, however, all the frequencies which were used as a basis for the calculation of the corresponding pulse duty ratios and come into consideration according to the result of the check in step 507 can be checked for their plausibility in a step 509. This plausibility check may in this case include checking the value range, obtained from the respective frequency, of the data transmitter. Similarly, changes in comparison with the previous data values can be evaluated with respect to the individual data transmitters. If this plausibility check in the step 509 reveals that only one of the frequencies coming into consideration on the basis of the check in the step 507 is can correspond to the information of a data transmitter, in the step 510 the frequency used in the calculation of the corresponding pulse duty ratio is evaluated in order to obtain the information of the corresponding data transmitter. otherwise, no information of a data transmitter can be obtained in this programme cycle.
Fig. 6 shows a f urther exemplary embodiment of a sequence of the method according to the invention, in which the frequency characterizes the data transmitter and the pulse duty ratio characterizes the data to be transmitted.
In the case of the flow chart shown in Fig. 6, the method of evaluating the signal level changes is described, this method being carried out immediately after establishing the positive signal level change at the point in time tio Then all the past points in time of signal level changes which lie in a time interval which corresponds to the maximum possible recurrence plus the time of the duration of the negative signal level of each of the three data transmitters are taken into consideration for the evaluation. The maximum possible recurrence in this case refers to the time interval which corresponds to the minimum possible frequency.
The flow chart shown is run through cyclically. For evaluation, past points in time which lie within the said time interval are required. Therefore, in the step 601 it is f irst of all checked whether points in time lying further back in the past, considered from the current time, than the said time interval are stored. If it is established in this check that such points in time are stored, in the step 602 these points in time are then erased in a manner corresponding to a stack memory which operates on the FIFO principle.
In the step 604, the current time is then stored as the point in time if a signal level change has been established in the step 603. Apart from the point in time, in this case the direction of the signal level change is also stored. 16 In the step 605, an evaluation of these measurement data then takes
place by initially determining each possible recurrence.
The description of the present exemplary embodiment in this case relates to the current time to the effect that in the step 605 the point in time tlo was assigned a positive signal level change. Since a positive signal level change was established at the point in time tlo, in the step 605 each time interval is calculated from the number of points in time of negative signal level changes (tot t2P t5r t6) in the said time interval. Consequently, the following time intervals are calculated:
tabst,Wil - tg - t6 = 1.5, tabst,w21 - t 9 - t5 = 2.7, t = 4.5, abst,w31 t9 - t2 tabst,w41 t 9 - to = 5.0. tabst,w12 t6 - t5 = 1.2, t abst,w22 t6 t2 = 3. 0, tabst,w32 t6 - to = 3.5, tabst,w13 t5 - t2 = 1.8, tabst,w23 t5 - to = 2.3, tabst,w14 - t2 - to = 0.5.
In the step 606, the calculated time intervals are compared with the recurrences possible on the basis of the data transmitters used. In the present exemplary embodiment. these values are equal to 3 or 4 or 5. If, in this case, one or more of the calculated time intervals lie(s) within a certain tolerance range around possible values for the recurrence, in the step 607 the pulse duty ratios are calculated. Otherwise, the signal level change could not be assigned to a data transmitter. The current run through of the flow chart of Fig. 6 is then aborted. If the tolerance range is assumed to be, for example, 0. 01, it is shown that the time intervals tabst,w41 and tabst,w22 come into consideration as a possible recurrence of the data 17 transmitters S1 and S2, respectively.
In the step 607, the pulse duty ratios f or the recurrences which come into consideration according to the check in the step 606 are calculated. Thus, the following pulse duty ratios are calculated, the figures in the last column concerning the values of the present exemplary embodiment:
ttasti = (tio - t9) / tabst,w41 = 0-2, ttast2 = (t10 - t6) / tabst,w22 = 0.83.
In the check corresponding to the step 608, the pulse duty ratio which can be assigned to a data transmitter is then selected. It emerges from the value of the possible recurrences that the transmitter concerned is the data transmitter S1 or S2, which transmit with a pulse duty ratio of 0.2 and 0.33, respectively. This pulse duty ratio is in this case subject to certain variations in order to be able to transmit the information of the data transmitter. If, for example, 0.06 is assumed for the possible range of the variations of the pulse duty ratio, it is shown that only the pulse duty ratio ttastl comes into consideration, since the pulse duty ratio ttast2 cannot come from the data transmitter S2.
If it emerges in the check in the step 608 that a plurality of pulse duty ratios come into consideration, it may further be attempted, for example, to establish definitively which is concerned from the changes of the respective data values with time.
Corresponding to the step 409, there then takes place in the step 609 an evaluation of this pulse duty ratio, in order to obtain the information of the corresponding data transmitter.
It is important in this case that both the frequency and the pulse duty ratio are evaluated, in order to be able to assign the information to the individual data transmitters.
18 It is readily evident that in the exemplary embodiments described above positive signal level changes may also be used instead of the negative signal level changes, in which case the positive signal level changes are also to be substituted by negative signal level changes.
A more reliable assignment of the signal level change to the data transmitters can be achieved in this case if the data transmitters are characterized by the pulse duty ratio. For this, under certain circumstances, the computing effort is less if the data transmitters are characterized by the frequency.
Since the data transmitters transmit stochastically onto the data line, under certain circumstances individual data values may be lost if - as described above - no assignment of a signal level change to a particular data transmitter is possible. Therefore, this method is suitable in particular for transmitting data values of slowly changing variables.
Fig. 7 shows a device for carrying out the method. A plurality of data transmitters SI, S2,..., Sn are connected to a preferably stabilized voltage supply UO via a series resistor Rv at the points 702, 703, 704 to the data line 701. In this case, the ohmic resistance effective on the data line 701 can be changed by each data transmitter, in that in each case a resistor RS 708, 709, 710 can be connected to earth by each data transmitter S1, S2,..., Sn by means of in each case a transistor 705, 706, 707. If a plurality of data transmitters switch simultaneously, there is consequently a parallel connection of the resistors RS1 i.e. a reduction in the ohmic resistance effective on the data line. Then the voltage on the data line 701 is evaluated by a computing device 711, in that the component voltage of the voltage UO dropping across the resistor Rv with a series connection of the resistor Rv and the parallel connection of the resistors Rs is fed to an A/D converter 712 connected to the computing device 711. From this component voltage, the voltage on the data line 701 and 19 conse-quently also the signal level changes can then be derived.
The number of connectable data transmitters is limited by transfer and contact resistances and, in the case of data transmitters of which the frequency lies between 1 and 2 kHz, may be about 5.
The data transmitters may in this case be correspondingly constructed sensors or else other data transmitters, such as for example computers which are networked by means of the data line.
Claims (6)
1. A method of transmitting data of a plurality of data transmitters on a common data line to a central receiving unit, in which method the data transmitters are in each case capable of two logical output states and the emission of pulse-width-modulated digital signals and are adapted in each case to be connected via a first resistor to the data line and data signals transmitted to the central receiving unit can be picked off there at a resistor at least contributing to termination of the data line, wherein - digital signals in the form of positive and negative signal level changes are transmitted by the data transmitters via corresponding first resistors simultaneously onto the data line, - jump-like signal level changes occurring in the quasianalogue sum signal resulting in this respect on the data line are sensed by the central receiving unit, - An the central receiving unit the current frequency and the current pulse duty ratio of the digital signal of each of the data transmitters are derived or recovered from the time intervals of past positive and negative signal level changes, and - the frequency in each case characterizes the data transmitter and the pulse duty ratio in each case characterizes the data value currently to be transmitted of the data transmitter concerned.
2. A method of transmitting data by a plurality of data transmitters on a common data line to a central receiving unit, in which method the data transmitters are in each case capable of two logical output states and the emission of pulse-width-modulated digital signals and are adapted in each case to be connected via a first resistor to the data line and data signals transmitted to the central receiving unit can be picked off there at a resistor at least 21 contributing to termination of the data line, wherein - digital signals in the f orm of positive and negative signal level changes are transmitted by the data transmitters via corresponding first resistors simultaneously onto the data line, - jump-like signal level changes occurring in the quasianalogue sum signal resulting in this respect on the data line are sensed by the central receiving unit, - in the central receiving unit the current frequency and the current pulse duty ratio of the digital signal of each of the data transmitters are derived or recovered from the time intervals of past positive and negative signal level changes, and - the pulse duty ratio in each case characterizes the data transmitter and the frequency in each case characterizes the data value currently to be transmitted of the data transmitter concerned.
3. A method according to Claim 1 or 2, wherein a running plausibility check of the information received from the data line and to be assigned respectively to individual data transmitters is carried out.
4. A device f or carrying out the method according to any one of the preceding claims. wherein - each data transmitter comprises a switchable isolating means, - by means of said isolating means the data line from each data transmitter is switchable with equal priority and at any time via the first resistor assigned to each data transmitter, to a reference potential, and - the central receiving unit comprises an A/D converter f or converting the quasi-analogue sum signal obtained from the data line into a digital signal which can be evaluated digitally for positive and negative signal transitions.
5. A method of transmitting data of a plurality of data 22 transmitters on a common data line to a central receiving unit, substantially as described herein with reference to and as illustrated in the accompanying drawings.
6. A device adapted to carry out the method according to claim 5.
1
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19924232995 DE4232995C2 (en) | 1992-10-01 | 1992-10-01 | Method for transmitting data from several data transmitters on a common data line and device for carrying out the method |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9319060D0 GB9319060D0 (en) | 1993-11-03 |
| GB2271255A true GB2271255A (en) | 1994-04-06 |
| GB2271255B GB2271255B (en) | 1996-04-03 |
Family
ID=6469371
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9319060A Expired - Fee Related GB2271255B (en) | 1992-10-01 | 1993-09-15 | Method of transmitting data from a plurality of data transmitters on a common data line |
Country Status (3)
| Country | Link |
|---|---|
| DE (1) | DE4232995C2 (en) |
| FR (1) | FR2696562B1 (en) |
| GB (1) | GB2271255B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0871037A1 (en) * | 1997-04-07 | 1998-10-14 | Siemens Aktiengesellschaft | Circuit arrangement for monitoring an electronic circuit |
| DE19717933A1 (en) | 1997-04-29 | 1998-11-05 | Thomson Brandt Gmbh | Circuit arrangement with an encoder and an evaluation circuit |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2019069A (en) * | 1978-04-06 | 1979-10-24 | Ncr Co | Multiprocessor system |
| GB2149626A (en) * | 1983-10-27 | 1985-06-12 | Otis Elevator Co | Communications system |
| US4780714A (en) * | 1985-07-19 | 1988-10-25 | Siemens Aktiengesellschaft | Selective voltage supply system for data network distributor |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2210936A (en) * | 1936-07-03 | 1940-08-13 | Siemens Ag | Apparatus for simultaneously measuring two magnitudes through a common line section |
| GB1262647A (en) * | 1968-05-17 | 1972-02-02 | Richards & Co Ltd George | Radio control system |
| CH583486A5 (en) * | 1975-02-28 | 1976-12-31 | Theimeg Elektronikgeraete Gmbh | |
| JPS5634256A (en) * | 1979-08-29 | 1981-04-06 | Fuji Electric Co Ltd | Data transmission system |
| DE3921744A1 (en) * | 1989-07-01 | 1991-01-03 | Bayerische Motoren Werke Ag | COMMUNICATION METHOD FOR A INTRODUCTION DATA BUS OF MOTOR VEHICLES |
-
1992
- 1992-10-01 DE DE19924232995 patent/DE4232995C2/en not_active Expired - Fee Related
-
1993
- 1993-09-15 GB GB9319060A patent/GB2271255B/en not_active Expired - Fee Related
- 1993-09-29 FR FR9311600A patent/FR2696562B1/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2019069A (en) * | 1978-04-06 | 1979-10-24 | Ncr Co | Multiprocessor system |
| GB2149626A (en) * | 1983-10-27 | 1985-06-12 | Otis Elevator Co | Communications system |
| US4780714A (en) * | 1985-07-19 | 1988-10-25 | Siemens Aktiengesellschaft | Selective voltage supply system for data network distributor |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9319060D0 (en) | 1993-11-03 |
| GB2271255B (en) | 1996-04-03 |
| DE4232995C2 (en) | 1994-07-07 |
| FR2696562A1 (en) | 1994-04-08 |
| FR2696562B1 (en) | 1995-01-20 |
| DE4232995A1 (en) | 1994-04-07 |
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| Date | Code | Title | Description |
|---|---|---|---|
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20000915 |