CA1196977A - Data transmission system via power supply line - Google Patents
Data transmission system via power supply lineInfo
- Publication number
- CA1196977A CA1196977A CA000433531A CA433531A CA1196977A CA 1196977 A CA1196977 A CA 1196977A CA 000433531 A CA000433531 A CA 000433531A CA 433531 A CA433531 A CA 433531A CA 1196977 A CA1196977 A CA 1196977A
- Authority
- CA
- Canada
- Prior art keywords
- power supply
- emergency
- terminal units
- signal
- data
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
- H04B3/54—Systems for transmission via power distribution lines
- H04B3/546—Combination of signalling, telemetering, protection
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L12/403—Bus networks with centralised control, e.g. polling
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B2203/00—Indexing scheme relating to line transmission systems
- H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
- H04B2203/5404—Methods of transmitting or receiving signals via power distribution lines
- H04B2203/5408—Methods of transmitting or receiving signals via power distribution lines using protocols
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B2203/00—Indexing scheme relating to line transmission systems
- H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
- H04B2203/5429—Applications for powerline communications
- H04B2203/5458—Monitor sensor; Alarm systems
Abstract
ABSTRACT OF THE DISCLOSURE
A data transmission system for transmitting data via a power supply line includes a central processing unit, and branch terminal units connected to the central proces-sing unit via the power supply line, through which a high frequency AC signal is synchronously mixed into the AC com-mercial frequency power supply cycle so that a specific operation can be performed and the actual condition of the terminal units can be sampled and monitored during a normal operation. Emergency data signals are transmitted from any of the terminal units in a time interval during an AC
power supply frequency cycle after the transmission of a polling signal and the terminal units engage in a contention for the transmission of the emergency data signals through the power supply line, the emergency data signals being received in the central processing unit during that time interval.
A data transmission system for transmitting data via a power supply line includes a central processing unit, and branch terminal units connected to the central proces-sing unit via the power supply line, through which a high frequency AC signal is synchronously mixed into the AC com-mercial frequency power supply cycle so that a specific operation can be performed and the actual condition of the terminal units can be sampled and monitored during a normal operation. Emergency data signals are transmitted from any of the terminal units in a time interval during an AC
power supply frequency cycle after the transmission of a polling signal and the terminal units engage in a contention for the transmission of the emergency data signals through the power supply line, the emergency data signals being received in the central processing unit during that time interval.
Description
The present invention relates to a data trans-mission system for the transmissiorl of data via a power supply line, the system controlling ~ranching terminal units connected to the power suppl~ line, while normal]y sur~e~-ing conditions of such termir,al units, by transmitting highfrequency AC signals to the P,C comlnercial frequency in the power supply line upon internally mixing them toge-ther.
Conventionally, any existing means for transmit-ting and receiving data usinq signals synchronized with AC commercial power supply frequencies via a power supply line can be easily and correctly synchronized, and can effectively offset any adverse effects from either noise or impedance occurring in synchronism with the AC commercial power supply frequencies, ancl as a :result, it effectively stabilized reliability in the data transmission system.
However, since the data t:ransmission speed is largely limited by the existing AC commercial power supply frequencies, all the data have to be transmitted at an ex-tremely slow speed, i.e. l b:t per cycle, and so a long period of time is required, i-or example, for collectively sampling data signals frorn mclny terminal units on line by polling.
It is an object of the present invention to miti-gate or even entirely overcome this disadvantage.
~5 According to the present :invention, there is pro-vided a data transmission system for transmi-tting data via a power supply line, the syst;em including a central pro-cessing unit, a plurality of branch terminal units connected to the central processing un:Lt via t:he power supply line, through which a high frequency AC s:Lgnal is synchronously mixed into the AC commercial frequency power supply cycle so -that a specific opera-tion can be performed and the actual condition of the terminal units can be sampled and monitored during a normal operation, wherein t:he data transmission system further comprises means for t:ransmitting emergency data signals from any of the terminal units in a time in-terval during an AC power supply frequency cycle af-ter -the transmission of a polling signal; means for causing the terminal units to engage in a contention for the transmis-sion of the emergency da-ta si.gnals through the power supply line; and means for receiving the emergency da-ta signals in the central processing uni.t during the time in-terval.
~ fter the data sampl.ing is executed by the pol-ling means, the specific AC commercial power supply fre-quency cycle period can be allocated for transmission of emergency data between a plurality of terminal units via contention, and as a result, any change of status occurring in the terminal units can qui.cXly be transmitted to the central processing unit using a slo~-speed transmission line, while all the control signals from the central pro-cessing unit can also be transmitted to each terminal unit without being held waiting.
The inventi.on will be more readily understood from the following description of p:rior art and of an em-bodiment of the present invention, which is given by way of example, with reference to the accompanying drawings, wherein:
Figure 1 shows a si.mplified diagram of a conven-tional data transmission system using the power line;
Figure 2 is a timing chart illustrating the exist-ing time division stationary allocation system;
Figure 3 is a timing chart illustrating -the exist-ing polling system;
Figure 4 shows a simplified block diagram of a typical composition including the CPU and terminal units as a preferred embodiment of the present invention;
Figure 5 is a flowchart describing operations of the central processing uni.t;
Figure 6 is a flowchart describing operations of the terminal units;
Figure 7 is a timing chart describing the rela-tionship between the data samples and the periods for re-ceiving and transmit-ting the contro:L command;
Figure 8 is a timing chart describing a typical ~,~
,~
'77 mode when the data is being sampled; and Figure 9 is a timing ehart describing -the re-covery process when an e~lergency signal collides with others.
Figure 1 shows a simplified diagram of a conven-tional sys-tem for transmitting data via a power supply line 3. A central processing unit (CPU) 1 transmits a eontrGl eommand to terminal units 2 via the power supply line 3 by turning switches on and off to execute any desiynated operation, for example, On~Off operations for power and illumina-tion, or it usually monitors and displays operative conditions of terminal units 2, for example, existing con-ditions of a power source, illumination, or sensors, or alternatively, it eauses an alarm to be generated in the case of an emergency. These terminal units 2 incorporate the self-selective funetion so that they can enter in-to operation only when speeifi.e signals are deteeted.
Actually, there are three signal transmission systems most widely available. The first is a method of contention, by which signal transmission ean be started upon contesting available channel lines as soon as sueh a need for signal transmission arises. The seeond is the time division stationary slot allocation system, which, as shown in Figure 2, activates the CPU 1 to output a specific code H in order to establish a system synchroniza-tion before either transmitting or receiving data 21 through25 to and from respeetive terminal units 2 via the pre-liminarily alloeated slots. The third is the polling system, which, as shown in Figure 3, activates the CPU 1 tu output signals Pl, P2, and P3, eaeh containing an address signal, while any of the terminal uni.-ts 2 seleeted by these signals ean feed back data sueh as Dl, D2, and D3.
In regard to the first, eontention, system, sinee there is no relationship of ~ynehronization between -the CPU 1 and the terminal units 2 and between these terminal units 2 themselves, signals from the latter may coincide with each other, causing a state of eonfusion to oceur and the entire system to eventually malfunction. I~ this occurs, since a considerable time must be spent before -the normal condition is restored, the CE~U 1 will be obliged to stop sending any control comrnand until ~he entire system is back -to a normally operative condition. If such a failure occurs, quick service advantages otherwise inherent in such a -trans-mission system will be los-t.
The second above-mentionecl systern, i.e. the tirne division stationary slot allocation system, also requires a long time to collect sampling data in each cycle if a large number of terminal unit:s 2 are employed, since the CPU 1 will also be obliged to stop sending the control com-mand until the next data are completely collected.
Conversely, the -third system, i.e. the polling sys~em, can collect sampling data ~ithin a very short time in each cycle without causing the CPU 1 to stop sending the control command and, thus, without any waste of time.
On the other hand, if any change should take place in the status of these terminal units 2 immediately after the polling system has collected sampling data, such a change cannot be read by the CPU 1 ~mtil the sampling da-ta has been collected from all the remaining terminal units 2.
This requires a rela-tively long duration of time as com-pared to other conventional systems.
The present invent~.on enables the provision of a system capable of quickly cletect:ing any change of status occurring in the terminal unlts 2 by transmitting data by synchronously mixing a high i-requency AC signal into the AC commercial power supply frequency of the power line.
Referring now to the preferred embodiment of the present invention shown in F;gures 4 to 9, in which com-ponents similar to those of ~igure 1 are indicated by the same reference numerals~ Figure 4 shows a simplified block diagram of a data transmissic~n system including the central processing unit ICPU) 1 and a plurality of the terminal units 2. Although only one t:erminal unit 2 is shown in the drawing, it is -to be understood that many of them can be connected in the system v a the power line 3.
~6~
The central processing UIIit 1 comprises a micro-processor ~, a transmitter 5, a receiver 6, a switching unit 7, a display unlt 8, and an alarrn unit 9. The switch-ing unit 7 has switches for instructiny the terminal units to perform ON~OFF operations. The display unit 8 displays the actual sta-tus of the terminal units 2 by means of light emitting diodes or by a cathode ray tube or lamps. The alarm unit 9 generates alarm sound~ for example, by buzzer, if any abnormal condition arises at: any of the connected terminal units 2. Each of the terrninal units 2 is also provided with a microprocessor 10, a transmitter 11, and a receiver 12. An addressing switch unit 13 in each ter-minal unit 2 provides each terminal unit 2 with a respective independent address. A sensor unit 14 confirms the opera--tion oE apparatus e.g. a motor 15, controlled by control means (not shown) the control means may be, for example, a load controller such as a relay 16 shown in Figure 4, which turns the motor 15 ON and OFF.
Figure 5 is a flowchart describing operations of the central processing uni-t 1, while Figure 6 is a flow-chart describing operations of the terminal units 2.
Normally, while no input is being fed from the switching unit 7, the CPU 1 periodically executes a data sampling operation via the polling sys-tem as described later.
In E'igure 7, symbols 31 to 34 respectively show the data sampling cycle. If one of the swit:ching units 7 corres-ponding to any desired terminal unit 2 is operated, an ON/OFF
control command will be transmittecL from -the CPU 1 to the designated terminal unit 2, the control command preferen-tially preceding all other data being sampledO Symbol 30 of Figure 7 shows a period in which such a control command is either transmitted or received, and during this period, all the data sampling operations are inhibited, which can be restored only after the control command delivery period is terminated.
As soon as the CPU 1 receives an input from the switching unit 7, the CPU outpu-ts the ON/OFF control command to the designated terminal un.it 2, which -then identifies whether the received ON~OFF control command has been ad-dressed to that particular one of the terrninal units, and if so, initiates control of t.he ON/OFF operation of the re~ated apparatus, i.e. the motor 15, and slmultaneously sends out an ACKNOWLEDGE sigr,al to the CPU 1. On receipt of this signal, the CPU 1 decodes .i-ts contents and then displays the existing condition of the designated terminal unit 2 in the display unit 8.
The period of time needed for the delivery of the control cornmand for the ON/OEF operation of the terminal unit is as described above, where the time actually needed for wait-ing until the command signal is oulputted corresponds to one da-ta sampling cycle, thus being so short in effect.
Figure 8 shows a ti.ming chart for the data sampling operation, which actually corresponds to one of the cases denoted by symbols 31 through 3~ of Figure 7. With refer-ence to the timing chart of ~'igure 8 and the flowcharts of Figures 5 and 6, the data sampl:ing operation is described below.
In Figure 8, symbo]. 35 represents a polling signal delivered from the CPU 1 to a spec:ific one of the terminal units 2. That terminal unit 2 first identifies that the polling signal has been addressed to that terminal unit
Conventionally, any existing means for transmit-ting and receiving data usinq signals synchronized with AC commercial power supply frequencies via a power supply line can be easily and correctly synchronized, and can effectively offset any adverse effects from either noise or impedance occurring in synchronism with the AC commercial power supply frequencies, ancl as a :result, it effectively stabilized reliability in the data transmission system.
However, since the data t:ransmission speed is largely limited by the existing AC commercial power supply frequencies, all the data have to be transmitted at an ex-tremely slow speed, i.e. l b:t per cycle, and so a long period of time is required, i-or example, for collectively sampling data signals frorn mclny terminal units on line by polling.
It is an object of the present invention to miti-gate or even entirely overcome this disadvantage.
~5 According to the present :invention, there is pro-vided a data transmission system for transmi-tting data via a power supply line, the syst;em including a central pro-cessing unit, a plurality of branch terminal units connected to the central processing un:Lt via t:he power supply line, through which a high frequency AC s:Lgnal is synchronously mixed into the AC commercial frequency power supply cycle so -that a specific opera-tion can be performed and the actual condition of the terminal units can be sampled and monitored during a normal operation, wherein t:he data transmission system further comprises means for t:ransmitting emergency data signals from any of the terminal units in a time in-terval during an AC power supply frequency cycle af-ter -the transmission of a polling signal; means for causing the terminal units to engage in a contention for the transmis-sion of the emergency da-ta si.gnals through the power supply line; and means for receiving the emergency da-ta signals in the central processing uni.t during the time in-terval.
~ fter the data sampl.ing is executed by the pol-ling means, the specific AC commercial power supply fre-quency cycle period can be allocated for transmission of emergency data between a plurality of terminal units via contention, and as a result, any change of status occurring in the terminal units can qui.cXly be transmitted to the central processing unit using a slo~-speed transmission line, while all the control signals from the central pro-cessing unit can also be transmitted to each terminal unit without being held waiting.
The inventi.on will be more readily understood from the following description of p:rior art and of an em-bodiment of the present invention, which is given by way of example, with reference to the accompanying drawings, wherein:
Figure 1 shows a si.mplified diagram of a conven-tional data transmission system using the power line;
Figure 2 is a timing chart illustrating the exist-ing time division stationary allocation system;
Figure 3 is a timing chart illustrating -the exist-ing polling system;
Figure 4 shows a simplified block diagram of a typical composition including the CPU and terminal units as a preferred embodiment of the present invention;
Figure 5 is a flowchart describing operations of the central processing uni.t;
Figure 6 is a flowchart describing operations of the terminal units;
Figure 7 is a timing chart describing the rela-tionship between the data samples and the periods for re-ceiving and transmit-ting the contro:L command;
Figure 8 is a timing chart describing a typical ~,~
,~
'77 mode when the data is being sampled; and Figure 9 is a timing ehart describing -the re-covery process when an e~lergency signal collides with others.
Figure 1 shows a simplified diagram of a conven-tional sys-tem for transmitting data via a power supply line 3. A central processing unit (CPU) 1 transmits a eontrGl eommand to terminal units 2 via the power supply line 3 by turning switches on and off to execute any desiynated operation, for example, On~Off operations for power and illumina-tion, or it usually monitors and displays operative conditions of terminal units 2, for example, existing con-ditions of a power source, illumination, or sensors, or alternatively, it eauses an alarm to be generated in the case of an emergency. These terminal units 2 incorporate the self-selective funetion so that they can enter in-to operation only when speeifi.e signals are deteeted.
Actually, there are three signal transmission systems most widely available. The first is a method of contention, by which signal transmission ean be started upon contesting available channel lines as soon as sueh a need for signal transmission arises. The seeond is the time division stationary slot allocation system, which, as shown in Figure 2, activates the CPU 1 to output a specific code H in order to establish a system synchroniza-tion before either transmitting or receiving data 21 through25 to and from respeetive terminal units 2 via the pre-liminarily alloeated slots. The third is the polling system, which, as shown in Figure 3, activates the CPU 1 tu output signals Pl, P2, and P3, eaeh containing an address signal, while any of the terminal uni.-ts 2 seleeted by these signals ean feed back data sueh as Dl, D2, and D3.
In regard to the first, eontention, system, sinee there is no relationship of ~ynehronization between -the CPU 1 and the terminal units 2 and between these terminal units 2 themselves, signals from the latter may coincide with each other, causing a state of eonfusion to oceur and the entire system to eventually malfunction. I~ this occurs, since a considerable time must be spent before -the normal condition is restored, the CE~U 1 will be obliged to stop sending any control comrnand until ~he entire system is back -to a normally operative condition. If such a failure occurs, quick service advantages otherwise inherent in such a -trans-mission system will be los-t.
The second above-mentionecl systern, i.e. the tirne division stationary slot allocation system, also requires a long time to collect sampling data in each cycle if a large number of terminal unit:s 2 are employed, since the CPU 1 will also be obliged to stop sending the control com-mand until the next data are completely collected.
Conversely, the -third system, i.e. the polling sys~em, can collect sampling data ~ithin a very short time in each cycle without causing the CPU 1 to stop sending the control command and, thus, without any waste of time.
On the other hand, if any change should take place in the status of these terminal units 2 immediately after the polling system has collected sampling data, such a change cannot be read by the CPU 1 ~mtil the sampling da-ta has been collected from all the remaining terminal units 2.
This requires a rela-tively long duration of time as com-pared to other conventional systems.
The present invent~.on enables the provision of a system capable of quickly cletect:ing any change of status occurring in the terminal unlts 2 by transmitting data by synchronously mixing a high i-requency AC signal into the AC commercial power supply frequency of the power line.
Referring now to the preferred embodiment of the present invention shown in F;gures 4 to 9, in which com-ponents similar to those of ~igure 1 are indicated by the same reference numerals~ Figure 4 shows a simplified block diagram of a data transmissic~n system including the central processing unit ICPU) 1 and a plurality of the terminal units 2. Although only one t:erminal unit 2 is shown in the drawing, it is -to be understood that many of them can be connected in the system v a the power line 3.
~6~
The central processing UIIit 1 comprises a micro-processor ~, a transmitter 5, a receiver 6, a switching unit 7, a display unlt 8, and an alarrn unit 9. The switch-ing unit 7 has switches for instructiny the terminal units to perform ON~OFF operations. The display unit 8 displays the actual sta-tus of the terminal units 2 by means of light emitting diodes or by a cathode ray tube or lamps. The alarm unit 9 generates alarm sound~ for example, by buzzer, if any abnormal condition arises at: any of the connected terminal units 2. Each of the terrninal units 2 is also provided with a microprocessor 10, a transmitter 11, and a receiver 12. An addressing switch unit 13 in each ter-minal unit 2 provides each terminal unit 2 with a respective independent address. A sensor unit 14 confirms the opera--tion oE apparatus e.g. a motor 15, controlled by control means (not shown) the control means may be, for example, a load controller such as a relay 16 shown in Figure 4, which turns the motor 15 ON and OFF.
Figure 5 is a flowchart describing operations of the central processing uni-t 1, while Figure 6 is a flow-chart describing operations of the terminal units 2.
Normally, while no input is being fed from the switching unit 7, the CPU 1 periodically executes a data sampling operation via the polling sys-tem as described later.
In E'igure 7, symbols 31 to 34 respectively show the data sampling cycle. If one of the swit:ching units 7 corres-ponding to any desired terminal unit 2 is operated, an ON/OFF
control command will be transmittecL from -the CPU 1 to the designated terminal unit 2, the control command preferen-tially preceding all other data being sampledO Symbol 30 of Figure 7 shows a period in which such a control command is either transmitted or received, and during this period, all the data sampling operations are inhibited, which can be restored only after the control command delivery period is terminated.
As soon as the CPU 1 receives an input from the switching unit 7, the CPU outpu-ts the ON/OFF control command to the designated terminal un.it 2, which -then identifies whether the received ON~OFF control command has been ad-dressed to that particular one of the terrninal units, and if so, initiates control of t.he ON/OFF operation of the re~ated apparatus, i.e. the motor 15, and slmultaneously sends out an ACKNOWLEDGE sigr,al to the CPU 1. On receipt of this signal, the CPU 1 decodes .i-ts contents and then displays the existing condition of the designated terminal unit 2 in the display unit 8.
The period of time needed for the delivery of the control cornmand for the ON/OEF operation of the terminal unit is as described above, where the time actually needed for wait-ing until the command signal is oulputted corresponds to one da-ta sampling cycle, thus being so short in effect.
Figure 8 shows a ti.ming chart for the data sampling operation, which actually corresponds to one of the cases denoted by symbols 31 through 3~ of Figure 7. With refer-ence to the timing chart of ~'igure 8 and the flowcharts of Figures 5 and 6, the data sampl:ing operation is described below.
In Figure 8, symbo]. 35 represents a polling signal delivered from the CPU 1 to a spec:ific one of the terminal units 2. That terminal unit 2 first identifies that the polling signal has been addressed to that terminal unit
2, and then samples the present status of its motor relay for encoding and delivering t:he answerback signal to the CPU 1 as an ACKNOWLEDGE signal 36. Symbol 37 represents an emergency signal fed from a dif~erent one of the ter-minal units 2, where said emergency signal is outputted from this other one of -the termina]. units in a specific timing after the polling signal 35 has been detected using line contention, and indicating that an abnormal condition exists in this other termina]. unit 2. Symbol 38 denotes the ACKNOWLEDGE signal output: from -the CPU 1 in responding to the emergency signal.
The CPU 1 recei~es the ACKNOWLE~GE signal from a designated texminal unit 2 for the polling, then displays the actual s-tate of that terminal ~mit 2 and generates an alarm in respect of the other termi.nal unit 2. The CPU
1, however, provides a period for permit-ting the sampled data to be received during a predetermined cycle. When the data received by the CPU 1 is identified as -the erner-gency signal, the CPU 1 outpu-ts the ACKNOWLEDGE signal to the terminal unit 2 which sen-t such an emergency signal to the CPU 1. The CPU 1 then changes the display contents and simultaneously generates an ala.rm.
If the terminal unit 2 receives an ins-truction to deliver the sampled data to other units, it first identi-fies whether an emergency signal should be output from it-self, and if found necessary, it sets a flag and outputs the emergency data to a speci.fic cycle position correspond-ing to the data receiving period of the CPU 1. On receip-t of the ACKNOWLEDGE signal frcm the CPU 1, the terminal unit 2resets and stops the output of the emergency signal.
Even when the CPU 1. has polled other terminal units 2, such an emergency si.gnal can be output very quic~ly by using the time slot available for sampling data.
The CPU 1 may subst.itute the terminal unit 2 which delivered the emergency signa.1 for the ACKNOWLEDGE 38, by polling said terminal unit 2. If no emergency signal is generated, neither the CPU ncr any terminal unit exchanges such an emergency signal, and. so they can dele-te the ACKNOWLEDGE period in order t.o perfor.m the next data sampling during a specific safety period.
Figure 9 shows a chart illustrating a recovery process from a coincidence between emergency signals from two terminal units 2A and 2B. In Figure 9, symbols 35, 35', 35'', and 35''' denote -the polling signals output from the CP~ 1 for normal data sampling operations, whereas symbols 36, 36', 36'', and 3~''' are the ACKNOWLEDGE data ou-tput from the corresponding terminal uni-ts 2. All -the emergency signals are preliminarily encoded so that -they cannot be decoded when coincident with each other. Actually, these signals can easily be encoded. For example, when emergency signals A and B coincide with each other a-t the position 40 of Figure 9, since the CPU 1 canno-t decode both signals, i-t polls the next data by ignoring these emeryency signals. As shown in -the Elc)wchart of Figure 6, -the termin~l units 2A and 2B which respectively generated -the emergency signals will con-tinuously out:put emergency signals if no ACKNOWLEDGE signal is fed from -the CPU 1, until they even-tually receive the ACKNOWLEDC;E signals by any means such as a random delay, or until t:he units themselves are sub-jected to the polling.
~ andom delay means enables the system to properlyad]ust the time needed for waiting to cause the intlended opera-tions to be repeatedly performed by using the random digit table. In the embodiment of the present invention, such a random delay operation corresponds to -the act of repeating operations while determining whether such an emer-gency signal should be output during the ensuing polling operations. Using this means, coincident emergency signals A and B can eventually be separated to allow only the normal emergency signal to be transmitted. In Figure 9, only the terminal unit A outputs an ernergency signal at the position 37', whereas the unit B outputs an emergency signal at the position 37''', and as a result, these units A and B respec-tively receive the ACKNOWI.ED(,E signals 38' and 38''' so that the system can recover ~-rom th~e effect of the coinci-dence. According to simulati~e operations using a computer, it was confirmed that the mean time can effectively be shortened unless there are many fractional numbers of the coincidence, although the mean time needed for recovering from the effect of the coinc:Ldence is dependent on the algorithm of the random number generation.
The embodiment of the present invention thus described in reference to the annexed drawings will ob-viously be suggestive of der:Lvations or modifications by those skilled in the art. Il: should be understoodl however, that the present invention i, not limited -to the preferred embodiment described above, hut may be varied within the spirit and scope of the following claims.
The CPU 1 recei~es the ACKNOWLE~GE signal from a designated texminal unit 2 for the polling, then displays the actual s-tate of that terminal ~mit 2 and generates an alarm in respect of the other termi.nal unit 2. The CPU
1, however, provides a period for permit-ting the sampled data to be received during a predetermined cycle. When the data received by the CPU 1 is identified as -the erner-gency signal, the CPU 1 outpu-ts the ACKNOWLEDGE signal to the terminal unit 2 which sen-t such an emergency signal to the CPU 1. The CPU 1 then changes the display contents and simultaneously generates an ala.rm.
If the terminal unit 2 receives an ins-truction to deliver the sampled data to other units, it first identi-fies whether an emergency signal should be output from it-self, and if found necessary, it sets a flag and outputs the emergency data to a speci.fic cycle position correspond-ing to the data receiving period of the CPU 1. On receip-t of the ACKNOWLEDGE signal frcm the CPU 1, the terminal unit 2resets and stops the output of the emergency signal.
Even when the CPU 1. has polled other terminal units 2, such an emergency si.gnal can be output very quic~ly by using the time slot available for sampling data.
The CPU 1 may subst.itute the terminal unit 2 which delivered the emergency signa.1 for the ACKNOWLEDGE 38, by polling said terminal unit 2. If no emergency signal is generated, neither the CPU ncr any terminal unit exchanges such an emergency signal, and. so they can dele-te the ACKNOWLEDGE period in order t.o perfor.m the next data sampling during a specific safety period.
Figure 9 shows a chart illustrating a recovery process from a coincidence between emergency signals from two terminal units 2A and 2B. In Figure 9, symbols 35, 35', 35'', and 35''' denote -the polling signals output from the CP~ 1 for normal data sampling operations, whereas symbols 36, 36', 36'', and 3~''' are the ACKNOWLEDGE data ou-tput from the corresponding terminal uni-ts 2. All -the emergency signals are preliminarily encoded so that -they cannot be decoded when coincident with each other. Actually, these signals can easily be encoded. For example, when emergency signals A and B coincide with each other a-t the position 40 of Figure 9, since the CPU 1 canno-t decode both signals, i-t polls the next data by ignoring these emeryency signals. As shown in -the Elc)wchart of Figure 6, -the termin~l units 2A and 2B which respectively generated -the emergency signals will con-tinuously out:put emergency signals if no ACKNOWLEDGE signal is fed from -the CPU 1, until they even-tually receive the ACKNOWLEDC;E signals by any means such as a random delay, or until t:he units themselves are sub-jected to the polling.
~ andom delay means enables the system to properlyad]ust the time needed for waiting to cause the intlended opera-tions to be repeatedly performed by using the random digit table. In the embodiment of the present invention, such a random delay operation corresponds to -the act of repeating operations while determining whether such an emer-gency signal should be output during the ensuing polling operations. Using this means, coincident emergency signals A and B can eventually be separated to allow only the normal emergency signal to be transmitted. In Figure 9, only the terminal unit A outputs an ernergency signal at the position 37', whereas the unit B outputs an emergency signal at the position 37''', and as a result, these units A and B respec-tively receive the ACKNOWI.ED(,E signals 38' and 38''' so that the system can recover ~-rom th~e effect of the coinci-dence. According to simulati~e operations using a computer, it was confirmed that the mean time can effectively be shortened unless there are many fractional numbers of the coincidence, although the mean time needed for recovering from the effect of the coinc:Ldence is dependent on the algorithm of the random number generation.
The embodiment of the present invention thus described in reference to the annexed drawings will ob-viously be suggestive of der:Lvations or modifications by those skilled in the art. Il: should be understoodl however, that the present invention i, not limited -to the preferred embodiment described above, hut may be varied within the spirit and scope of the following claims.
Claims (3)
1. A data transmission system for transmitting data via a power supply line, said system including a cen-tral processing unit, a plurality of branch terminal units connected to said central processing unit via the power supply line, through which a high frequency AC signal is synchronously mixed into the AC commercial frequency power supply cycle so that a specific operation can be performed and the actual condition of the terminal units can be sampled and monitored during a normal operation, wherein said data transmission system further comprises:
means for transmitting emergency data signals from any of said terminal units in a time interval during an AC power supply frequency cycle after the transmission of a polling signal;
means for causing said terminal units to engage in a contention for the transmission of said emergency data signals through said power supply line; and means for receiving said emergency data signals in the central processing unit during said time interval.
means for transmitting emergency data signals from any of said terminal units in a time interval during an AC power supply frequency cycle after the transmission of a polling signal;
means for causing said terminal units to engage in a contention for the transmission of said emergency data signals through said power supply line; and means for receiving said emergency data signals in the central processing unit during said time interval.
2. A data transmission system as claimed in claim 1 wherein said central processing unit comprises means res-ponsive to any one of said emergency data signals for trans-mitting to the respective one of said terminal units an emergency acknowledgement signal addressed thereto and said emergency signal transmitting means comprise means for main-taining the transmission of the emergency data signal until the respective terminal unit receives one of said emergency acknowledgement signals addressed thereto.
3. A data transmission system as claimed in claim 2 wherein said maintaining means include means for effecting random delay in successive transmissions of the respective emergency data signal.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP57133932A JPS5925536A (en) | 1982-07-30 | 1982-07-30 | Power line data transmission system |
| JP57-133932 | 1982-07-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1196977A true CA1196977A (en) | 1985-11-19 |
Family
ID=15116439
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000433531A Expired CA1196977A (en) | 1982-07-30 | 1983-07-29 | Data transmission system via power supply line |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4611274A (en) |
| EP (1) | EP0100668B1 (en) |
| JP (1) | JPS5925536A (en) |
| CA (1) | CA1196977A (en) |
| DE (1) | DE3376612D1 (en) |
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| US4866602A (en) * | 1983-11-02 | 1989-09-12 | Microsoft Corporation | Power supply for a computer peripheral device which positions a cursor on a computer display |
| DE3402076A1 (en) * | 1984-01-21 | 1985-08-01 | Philips Patentverwaltung Gmbh, 2000 Hamburg | METHOD AND ARRANGEMENT FOR DATA TRANSFER |
| JPS6194433A (en) * | 1984-10-15 | 1986-05-13 | Mitsubishi Electric Corp | Control system for serial bus |
| US4910655A (en) * | 1985-08-14 | 1990-03-20 | Apple Computer, Inc. | Apparatus for transferring signals and data under the control of a host computer |
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| US4912627A (en) * | 1985-08-14 | 1990-03-27 | Apple Computer, Inc. | Method for storing a second number as a command address of a first peripheral device and a third number as a command address of a second peripheral device |
| US4875158A (en) * | 1985-08-14 | 1989-10-17 | Apple Computer, Inc. | Method for requesting service by a device which generates a service request signal successively until it is serviced |
| US4751495A (en) * | 1986-01-28 | 1988-06-14 | Raychem Corporation | Analog pulsed heat trace monitor or the like |
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| US4716409A (en) * | 1986-07-16 | 1987-12-29 | Homestead Products, Inc. | Electrical appliance control system |
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| CH677568A5 (en) * | 1989-03-21 | 1991-05-31 | Datawatt Bv | |
| FR2656188B1 (en) * | 1989-12-18 | 1996-10-18 | Telediffusion Fse | WIRED NETWORK INSTALLATION FOR PROGRAM DISTRIBUTION AND DIGITAL AND TERMINAL COMMUNICATION FOR SUCH AN INSTALLATION. |
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| EP0489944B1 (en) * | 1990-12-08 | 1995-09-20 | Deutsche ITT Industries GmbH | Master-slave data communication method with flexible one-wire bus |
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| KR100261512B1 (en) | 1998-06-17 | 2000-07-15 | 김철 | Remote control method using bidirectional power-line communication |
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| US20030189495A1 (en) * | 2002-04-03 | 2003-10-09 | Pettler Peter R. | Method and system for controlling a selected electrical load in a building |
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| JP5114329B2 (en) * | 2008-07-22 | 2013-01-09 | 京楽産業．株式会社 | Network system for game hall using PLC communication |
| JP5114330B2 (en) * | 2008-07-22 | 2013-01-09 | 京楽産業．株式会社 | Network system for game hall using PLC communication |
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| US4063220A (en) * | 1975-03-31 | 1977-12-13 | Xerox Corporation | Multipoint data communication system with collision detection |
| US4161786A (en) * | 1978-02-27 | 1979-07-17 | The Mitre Corporation | Digital bus communications system |
| DE2844453A1 (en) * | 1978-10-12 | 1980-04-24 | Bbc Brown Boveri & Cie | Transmission system for remote-control signal-packets - reduces cycle times by having substations distribute transmissions over several interrogations |
| CA1151261A (en) * | 1979-01-05 | 1983-08-02 | Jules M. Kabat | Two-way ac power line communication system |
| US4429299A (en) * | 1979-01-05 | 1984-01-31 | Robertshaw Controls Company | Two-way AC power line communications system |
| US4377804A (en) * | 1979-10-31 | 1983-03-22 | Matsushita Electric Works, Ltd. | Synchronous data transmission system utilizing AC power line |
| US4283529A (en) * | 1980-03-03 | 1981-08-11 | Abbott Laboratories | 3-O-Demethyl derivatives of Sannamycin C and antibiotic AX-127B-1 |
| JPS5767355A (en) * | 1980-10-15 | 1982-04-23 | Nec Corp | Data transmission controlling system at loop transmission system |
| US4447872A (en) * | 1980-10-20 | 1984-05-08 | Minnesota Mining And Manufacturing Company | Alarm data concentration and gathering system |
| US4379294A (en) * | 1981-02-12 | 1983-04-05 | Electric Power Research Institute, Inc. | Data highway access control system |
| US4439856A (en) * | 1982-02-24 | 1984-03-27 | General Electric Company | Bimodal bus accessing system |
-
1982
- 1982-07-30 JP JP57133932A patent/JPS5925536A/en active Pending
-
1983
- 1983-07-29 DE DE8383304412T patent/DE3376612D1/en not_active Expired
- 1983-07-29 CA CA000433531A patent/CA1196977A/en not_active Expired
- 1983-07-29 EP EP83304412A patent/EP0100668B1/en not_active Expired
- 1983-07-29 US US06/518,450 patent/US4611274A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0100668B1 (en) | 1988-05-11 |
| EP0100668A3 (en) | 1985-08-07 |
| DE3376612D1 (en) | 1988-06-16 |
| JPS5925536A (en) | 1984-02-09 |
| EP0100668A2 (en) | 1984-02-15 |
| US4611274A (en) | 1986-09-09 |
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