DE2339084C3 - Data station and data switching system - Google Patents

Description

The invention relates to a data station according to claim 1 and a data switching system, which is equipped with such data stations and a central data processing machine.

The transmission of data for purposes of control, display or storage often requires the Signal exchange between a large number of data stations and a central data processing machine.

The from each other and from the data processing machine Remote data stations can conventionally each have their own transmission channel be connected to the central data processing machine. With such a structure the connection channels devour a high proportion of the total costs of the system. Furthermore is there is a practical limit to the total number of data stations. - Every single data station must be polled or addressed separately by the data processing machine. If at such a If the total number of data stations is very large, this can overload the central data processing machine as a very large proportion of the total available central processing time is used for the polling and addressing operations of the terminals.

A brief explanation of the terms "pollen" and "addressing" should be given at this point. Polling means that the central data processing unit sends a signal to a data station in order to determine whether this data station is suitable for transmission keeps pending data ready for the head office. The term "addressing" means that the central data processing machine Has to transmit data to one or more of the data stations.

Another structure for connecting the remote data stations has also become common, in which the cost of the connection channels are reduced. A number of data stations are divided into one common connection channel to the central data processing machine. With the basic form Such a structure must in turn each data station by the data processing machine of the central station polled or addressed.

A further development of this structure is described in US Pat. No. 3,668,649. After that it is already no longer necessary, each individual data station within one of the intended chain connections polling to determine whether there are messages to be transmitted or not. It is enough after this US-PS to address any of the data stations on the common connection channel. Has a disadvantageous effect however, all of the stations provided on the common connection channel are now competing are available for transmission. To this end, logical precautions must be taken to ensure that only one data station can transmit at a time and only after its end can another one Station begins. The problem of competition arises again and again, and so on also not possible to give a certain station a polling priority on the common channel to be issued as determined by the headquarters. This is another disadvantage.

To reduce the time required by the central station when polling the individual data stations, the so-called closed loop techniques have been proposed. All data stations are here arranged in a closed loop In the simplest form, the central station sends a poll signal via the loop, and the first data station within the loop to be queried picks up the poll signal and then transmits its pending messages to the central station. If the operation of this data station then finished, it sends a poll signal on over the loop. With such a structure is for the individual data stations are given a certain order of priority, which in the following position of the individual Data stations within the loop is established.

Various techniques have been proposed for making such a loop system to give more flexibility to the order of priority. To this end, it was proposed that the to send data to be transmitted in different directions over the loop.

Another way to control the traffic in a polling loop was through the DT-OS 2 056 832 known. According to this release, a check is made to see if a workstation is in the loop There are transmitted messages pending, and a tone signal to issue the transmission permission on the part of the central station sent out. This sound signal is passed through all stations through to the last one and reverses there via a special filter device that only lets the audio signal through, but not the data signals. On the return line, the audio signal now reaches the data station that is furthest away with pending messages to be transmitted first. This starts first with the transfer. To at the end of the transmission, the terminating data station allows the sound signal to continue to return to the next station furthest away, which can then begin. The disadvantage here is that in addition to the Provision of special audio signal transmission, filtering and evaluation means each call is passed through to the very last station and from there only comes back. It is therefore not possible to use one of the between the control center and the last one outside Call the external station arranged by the station, if necessary, with priority. For very long canals has a further disadvantageous effect that such a polling call in the form of a tone signal only covers the entire Run time to the furthest end and from there back to the next transmitting station.

All of these construction options described above have significant disadvantages when an additional Data station is to be looped into an existing system. In particular, there are difficulties to be expected if within an existing loop with device supplied by a manufacturer a data station supplied by another manufacturer is to be inserted or if related to

the priorities have special requirements.

The object of the present invention is to specify a data station, with the help of which an opposite The aforementioned systems can be operated more flexibly and more efficiently, which saves po! l and addressing time is.

The solution to this problem is made possible with the aid of a data station, which is defined by claim 1 is marked.

Advantageous configurations of the data station and data switching systems equipped therewith are shown in the subclaims described.

With the data stations according to the present invention and a data exchange system constructed therewith the disadvantages of the above-mentioned older publications are avoided in an advantageous manner. First, there is no contention between the individual terminals on a common channel given that would have to be handled by special logic switching means. Furthermore will normally the most distant station is generally given permission to transmit first and by Rolling up there backwards only the stations requesting the further connection. A competition problem is thus avoided from the outset. On the other hand, no special sound signal processing means are used required for pollen and permission to transmit. The long way to the last outdoor station and back from there is avoided. - The main advantage of a system according to the present invention can be seen above all in the fact that data stations are located between the control center and the last outstation can be polled with priority.

Embodiments of the invention are shown in the drawings and will be described in more detail below explained it shows

F i g. 1 shows the block diagram of a conventional data switching arrangement with a central data processing machine CPU and a large number of remote data stations T,

F i g. 2 the block diagram of a modification of such a system in which some data stations are chained are,

F i g. 3 shows the block diagram of a system similar to that according to FIG. 2 and

F i g. 4 shows the block diagram of a data station for a system according to FIG. 3.

According to FIG. 1, a central data processing machine 1 is connected to six remote data stations 2 to 7 via a channel 8 in which all the data stations provided are shared. All data stations are arranged at different places, although, as shown in the drawing, place 9 has two data stations 2 and 3 which are connected to the common channel 8 via two stub lines 10 and U, respectively

During operation, the central data processing machine 1 sends a separate polling signal to each of the data stations, all of which are labeled T, to determine whether one of the individual stations has data to be transmitted to the central station with the data processing machine 1. If z. B. the terminal 4 is polled and this data has to be sent to the central station, the terminal 4 sends a signal to the central station to indicate that it is ready for data transmission . When the data processing machine 1 receives a signal EOT = "end of transmission" from the data station 4, the next data station is polled,

z. B. the data station 5. If the data station 5 has no data to be transmitted, it leaves this Central station know so that it can poll the next data station in turn.

It may be expected that some of the

ίο provided data stations more often with the central station Have to take up traffic; they should be given a higher priority. The internal circles the data processing machine 1, which can be microprogrammed, determine how often each Data station is polled.

If the data processing machine 1 has data pending to be sent to one of the data stations, e.g. B. Station 7, are to be transmitted, this data station 7 is controlled by the data processing machine t in the central station addressed. Then the data is transferred to station 7. Either the data processing machine can 1 wait for a return signal from the addressed data station, which indicates that the data station the data processing machine is or can be ready to receive data immediately transmit the data to be transmitted and then the return or non-return wait for an acknowledgment signal from the addressed data station in order to be able to recognize whether or not the transmitted data have been received by the addressed data station.

Systems operating in this way are relatively simple; the time required by the data processing machine 1 in the central station to poll and address the data stations increases with the number of data stations that are connected in total. The time remaining for the data processing machine 1 for internal operations is thus significantly limited
Although the performance of the data processing machine 1 could of course be increased in order to serve a large number of data stations, there is still another factor which keeps the total number of data stations that can be connected within limits . In Great Britain e.g. B. no more than 12 data stations are allowed on a common channel

F i g. 2 shows a modification of the system according to FIG. 1, with which this problem can be dealt with in a certain way. According to FIG. 2, instead of the branch channels 10 and 11, only one common branch channel 16 is provided, which is connected via a modem 15. With this modem 15, the data stations 12, 13 and 14 are connected in a chain-like manner. Are counted by the postal administration is 15 counted this modem as a Daiensta tion connection whereas the individual Since tenstationen 12 not separately to 14. Thus, for the three terminals 12, 13 and 1 'at the position 9, only a single branch channel 16 to the fo the entire system common channel 8 is connected. This advantage is bought with the Odem 15

The overload of the central data processing machine 1 by polling and addressing has not been improved, however, since the individual data stations are again in the same way as at Ham F i g. 1 are to be polled and addressed.

F i g. 3 now shows a data switching system according to the present invention. The data stations 4, 5 and 6 and data stations in the more distant locations 9 and 20 can again be reached by the central data processing machine 1 via the common channel 8. At the point 9, the data stations 12, 13, 14 and 21 are connected to the channel 8 via a modem 15 and at the point 20 the data stations 17, 18 and 19 are connected together to the channel 8.

The polling and addressing of the data stations 4, 5 ″ and 6 is carried out in a manner similar to that already described above; no further explanation is given in this regard. However, data terminal 21 at location 9 and data terminals 17, 18 and 19 at location 2ΙΪ are polled and addressed in a different manner, which will now be described. Therefore, these special stations are labeled T.

To poll the data stations 17, 18 and 19, the file processing machine 1 sends a poll signal via the channel 8 to the last data station in the chain, namely to the data station 19. This poll signal is not transmitted in the usual way by the data stations

17 and 18 (exceptions to this will be described later), but rather transmitted through them to the data station 19. When the data station 19 has to transmit data to the central station, it connects to the file processing machine 1 in the central station and begins its data transmission through the Data stations 17 and 18 through. At the end of the transmission, the data station 19 sends an EOT-Si 3 <> signal to the data processing machine 1.

If the data station 19 does not have to send any data to the central station when polling, it instead sends a false indication signal NRS to the data processing machine 1 in the central station.

The data stations 17 and 18 recognize this false indication signal or the EOT signal, which comes from further back in the chain, and evaluate it as a poll signal. When the data station 18 receives an EOT or NRS from the data station 19, it thus inserts its own data into the data processing machine 1, if necessary, and only then lets this EOT or NRS through. The data station 17 now recognizes the EOT or NRS from the data station 118 in a similar manner and can, if necessary, proceed with its own data in the same way as before for the data station

18 was described.

The data processing machine 1 in the central station thus receives successively from the station 20 Data from the terminal 19, from the terminal

18 and from the data station 17. All these data are only received in response to the single poll signal that was directed to the data station 19. The data stations 17 and 18 therefore do not need to be polled individually , as is the case with the systems according to FIG. 1 and 2 is required

The addressing functions also differ from those already described. If the data processing machine 1 to all data stations 17, 18 and

19 has to be transmitted, their data are summarized and transferred to position 20. The individual parts of the total data stream are provided with the special addresses of the individual data stations to which they are directed. Each of the data stations 17, 18 and 19 recognizes from these addresses which part of the data stream is directed to itself, and accepts the corresponding data for itself. It is irrelevant whether the individual data stations such. B. 17 or 18 absorb the passing data completely from the data stream or not. Each of the data stations will only evaluate the part of the data stream that is actually addressed to itself.

When a data station has recognized the data addressed to it, it generates an identification signal as to whether the recorded data was received properly or whether the message was received garbled became. This identification signal is transmitted to the data processing machine 1 when the the station in question will be polled the next time. When a station does not get its data properly received because z. B. the address was garbled, sends it to the next polling by the data processing machine 1 no acknowledgment signal returned. if the data processing machine 1 receives a signal from the data station that a garbled message or if it does not receive any return signal, it tries to address the relevant one again Data station.

The data processing machine 1 can of course be set up so that it recognizes when one of the data stations is disturbed and the data processing machine continues with no return signal or only Receives error return signals.

To summarize again: the data stations 17 and 18 receive when they are addressed. Data from the data processing machine 1. However, they do not pick up poll signals from the data processing machine in the usual way. They are polled either by an EOT or an NRS signal from the last data station in the chain or from a data station further back in the chain

At the point 9, a data station 21 is inserted between the data stations 12 and 13. The data stations 12, 13 and 14 operate as first described; they are polled and addressed individually.

The data station 21, however, works like the data stations 17 and 18. 21 does not respond immediately to a poll signal, but waits for an EOT or NRS signal that is directed from further down the chain to the data processing machine 1 and 14 are polled individually, 21 will also be polled effectively Everything else remains unchanged; d. This means that the data station 21 is always polled as often as the data stations 13 and 14 together.

A simple pre-authorization of the data station 21 with regard to the priority is thus possible. If it is a data station with very high priority, it can be placed in the chain between the modem 13 and the data station 12. It is then automatically polled every time one of the other data stations in the entire chain is polled. If, on the other hand, it is a data station with lower priority, it can be arranged between the data stations 13 and 14. Then it is only polled once each time together with the data station 14

The method of addressing data terminal 21 depends on the method of polling the other data stations in the chain. If z. B. the data Stations 12, 13 and 14 are individually addressable who the data to the data stations 13 and 14 together with those for the data station 21 in one stream grasps

A variation would be possible when addressing, in

ίο

which all data stations of the station 9 are addressed at the same time will. In other words: there are then data for the data stations 12, 13, 14 and 21 in one Stream sent from the data processing machine 1 to the point 9, where the individual data stations their Remove individual parts of the message as has already been described for position 20.

One advantage of the system described is the possibility of a data station, such as B. 21, to be retrofitted in an existing system.

Often z. B. different areas of work of a bank or banks for subscriber operation with a central data processing machine verbun the. For each individual line of business, the to make the necessary data processing capacity available in the head office without having to deal with each individual Branch of business to require its own computer. Typical data stations already installed at banks are printers, keystrokes, visual display devices, etc. are not yet so common at Banks currently use data terminals in the form of cash dispensers. The purpose of such having a central office connected cash dispensers is to relieve the bank counters and cashiers of the at the deposit of checks and / or to enable cash withdrawals as well after bank close. In the case of a connected cash dispenser, the interested customer guides normally a code card into the terminal and also enters a personal identification number using a small keyboard. Before the Output of cash amounts to this customer connects the data station with the remote data processing machine, to z. B. to check whether the code card is about blocked, and against the account balance of the customer to consider.

Such connected cash dispensing devices are now being introduced at banks; the present invention is an aid to facilitate this the insertion of such cash dispensing devices into existing data switching systems with a minimum of trouble. This is especially important if the already installed Device was supplied by a different manufacturer.

In the description of FIG. 3 it was already clear that the chained data stations in positions 9 and 20 depend essentially on the other data stations.

At the point 20 z. B. need the data stations 17 and 18 a returning signal from the data station 19 to be polled themselves. Furthermore, poll signals and data are transmitted through the data stations 17 and 18 to the data station 19. If one of the data stations at point 20 should be disturbed, then the other data stations will also be affected more <x> er less M-jrk, depending on the type of disturbance.

If z. B. the data station 19 is disturbed and no special precautions have been taken, the data stations 17 or 18 could not be polled. Although they could be addressed by the data processing machine, the central station would never be able to receive confirmation that the data sent to it were correctly received.

For this reason, the data stations should preferably be provided with facilities that can counteract such error circumstances. These facilities are shown in detail on the basis of FIGS. 4 described. Precautions are taken to bridge a failing data station within the chain, and also to call the last still functional data station within such a chain as the last chain data station if the actual last data station in the chain has failed.

ίο F i g. 4 shows the block diagram of the data station 21, the same for the data stations 17, 18 and 19 gill. The data station 21 contains an input / output device 22, with the help of which messages can be input or output via the data station in question.

The I / O device 22 is connected to a buffer 24. Control circuits 26 are used to control the run of data and other signals within the data station. In addition, these control circuits can do the compilation and other handling of data within the data station independently of the central one Perform data processing machine.

The data station 21 contains a receiver 28 for receiving data from the central data processing machine and a transmitter 30 for transmitting data and signals to further back in a considered Data stations arranged in a chain. The task of the link 32 and the decoder 34 will be described later. The data station also contains a receiver 36 for receiving data and signals from data stations further down the chain and a transmitter 38 for transmission of data and signals to the central data processing machine. The task of the links 40 and 44 and the decoder 42 will be described later.

It is assumed that a poll signal is received from the central data processing machine. This normally enters the receiver 28 and continues to the transmitter 30 via the link 32. From there it is forwarded to the next data station located further back in the chain. Thereupon comes either an NRS signal from further back or, according to the transmitted data signals, an EOT signal, which is recorded in the receiver 36. The NRS or EOT signal is decoded in the decoder 42. The control circuits 26 then ensure the transmission of data in the buffer 24 via the logic element 44 and the transmitter 38. These data are transmitted to the central data processing machine before the aforementioned NRS or EOT signal is transmitted via the logic element 40 under the control of the control circuits 26 is transmitted in the direction of the central data processing machine.

When addressing, the incoming data stream is recorded by the receiver 28. When the Dc coder 34 recognizes its own address in this data stream, the part of the de: data stream belonging to this address for the data station 21 is transferred to the buffer 24 via the link 32 under the control of the control circuits 2. This data can then be output by the I / O device. The data stream with or without the viewed data for dv station 21 is transmitted on via transmitter 30 to the next data station in the chain.

When data from the central data processing machine is received by the data station 2 in this way, the control circuits cause 26 dii

Generation of a signal which is sent to the central data processing machine during the next following poll cycle is transmitted, namely as soon as the next NRS or EOT signal by the decoder 42 is recognized.

Let us now assume that the last data station in the chain fails. Then no NRS or EOT signal will be recognizable by the decoder X1 and the data station 21 will not be polled. However, as shown in FIG. 4, the data station 21 only operates normally when it receives a ready signal B from the last data station in the chain, which indicates (for example in the form of a DC voltage signal) that the last data station is ready for operation. As soon as the data station following the data station 21 fails, the ready signal B no longer arrives. Under the control of the control circuits 26, the data station 21 itself now acts as the last chain data station. In other words: the absence of the incoming ready signal B causes the data station 21 to automatically respond to poll signals that are received by the receiver 28, as if the data station 21 itself were the last chain data station. The data station 21 then also generates either an NRS signal or, after its own data transmission, an EOT signal. The same applies to the last data station i9, which is normally the last chain station anyway and does not receive a B signal from further back.

The data station 21 normally transmits the B signal further in the direction of the central data processing machine. If the data station 21 should fail, the next data station arranged further ahead in the chain is thus indicated that it must now take over the role of the last chain data station. Furthermore, circuits 46 are provided for bypassing in the event of the failure of the data station 21, with the aid of which forward polling signals and the ready signal B can be transmitted from backward to data terminals arranged further forward. This avoids any disadvantage to the further data stations arranged behind the data station 21. The bypass circuits 46 can be turned on either manually or automatically.

The exemplary embodiment is described using a system with a central data processing machine and several remote data stations. However, individual or all of these data stations can in turn be connected to a concentrator be. This concentrator can itself have data processing capabilities or with a work together within the network under consideration external data processing machines.

Furthermore, the data exchange system under consideration can either only serve chains as in the Position 9 in FIG. 3, which contain individually pollable data stations, or chains as in point 20 according to F i g. 3 or also a mixed arrangement of chains of both types. It is essential that in the Chains data stations can be connected to the system that do not have separate pollen or conventional ones Require addressing. From a postal administration standpoint, chain 20 has either three data stations switched on or, if channel 8 via a modem, as in position 9 with the chain connected, only a single countable terminal.

For this purpose 3 sheets of drawings

Claims (12)

Patent claims: 1. Data station for a data switching system with a first receiver and a first transmitter, which form a first, independently operable interface for processing the data exchange under alternating or counter operation with a central data processing machine arranged remotely in the common network, and with a second transmitter and a second receiver, which form a second interface for data exchange with alternating or opposing operation with an adjacent data station and for further transmission of data from this neighboring data station to the central data processing machine or vice versa, characterized by a selective coupling option for the output of the first receiver (28) with the input of the second transmitter (30) and for the output of the second receiver (36) to the input of the first transmitter (38); by a first decoder (42). The input of which is connected to the output of the second receiver (36) for monitoring signals received from the neighboring data station (T, T) which are further away from the central data processing machine (1) in terms of transmission and which are transmitted according to the same method that is also used for the transmission of data in the system is used, and to identify when no or no more data are to be transmitted to the central data processing machine (1) from the neighboring data station (T, T ') or a data station (T, T') that is further away in terms of transmission; and by control circuits (26) connected to the output of the first decoder (42) for coupling the first receiver (28) to the second transmitter (30) and the second receiver (36) to the first transmitter (38) for the continuous data exchange between the first and second interfaces and to initiate the data station's own data transmission (T. T '), if there is data to be transmitted, as well as to forward a signal "END OF TRANSMISSION" (EOT) or to transmit a signal »NO DATA« (NRS) if there is no data to be transmitted by the station itself. 2. Data station according to claim 1, characterized by a second decoder (34) for monitoring data received from the central data processing machine (1) and for detecting when these received data are addressed to the data station (T, T ') itself. 3. Data station according to one of the preceding claims, characterized by circuits for detecting whether a further data station (T, T ') connected subsequently via the side facing away from the central data processing machine (1) is ready for operation, and circuits for initiating its own data transmission to the central data processing machine (1) in response to a poll signal from this if no further operational data station (T, T ') can be recognized on the opposite side. 4. Data station according to one of the preceding claims, characterized by circuits for transmitting a ready signal (B) in the direction of the central data processing machine (1), if the data station (T, T ') is ready for operation. 5. Data station according to one of the preceding claims, characterized by switching paths (46) for selectively bypassing the data station (T, T ') 6. Data switching system using data stations according to one of the aforementioned Claims is built up with at least one to a central data processing machine connected transmission channel and at least one data station at the remote end of the transmission channel, characterized by at least one chain-like intermediate Data station (IZ 21,13; 17,18) between the central Data processing machine (1) and the data station (14, 19) provided at the end of the channel; Provisions in the central data processing machine (1) for sending a poll signal to the last data station (14, 19) at the physical end of the channel or a specific poll signal the data station at a selectable channel end that is selectively between the central data processing machine (1) and the physical end of the channel can be determined: and precautions in all interlinked Data stations (12, 21, 13; 17, 18) for your own transmission of data from these data stations (12, 21.13; 17.18) to the central data processing machine (1). if a signal (NRS or EOT) is received from the direction of the current end of the channel, which makes it clear that it is off Direction from the end of the channel, there is no more data or no more data waiting to be transmitted, and if in the data station (12. 21, 13: Ί7. 18) itself data to be transmitted are available. 7. Plant according to claim 6, characterized by additional provisions in the central data processing machine (1) and additional circuits in the interlinked data stations (12, 21, 13; 17, 18) and the data station (14, 19) on Channel end for individual addressing of the individual data stations for chain output of data streams from the central data processing machine (1) to the individual Data stations (12.21.13.17.18; 14.19). 8. Installation according to one of claims 6 or 7, characterized by switching paths for bypassing (46) of the interlinked data stations (12, 21, 13; 17, 18) in the event that at least one interlinked Data station fails. 9. System according to one of claims 6 to 8, characterized by circuits in all data stations (12, 21, 13, 17, 18; 14, 19) to display the own operational readiness to the next in Data station and circuits arranged in the direction of the central data processing machine (1) in all interlinked data stations (12,21,13; 17,18) for answering a received Pollsignals if all subsequently via the from the central data processing machine (1) facing away from the connected data stations cannot be seen ready for operation. 10. Plant according to one of claims 6 to 9, characterized by at least one chain arrangement several data stations (17, 18, 19), all of which on a common assigned poll signal one after the other address and, if necessary, send pending data. 11. System according to one of claims 6 to 10, characterized by several data station chains (12. 21,13, 14; 17,18,19), their individual data stations (12,13,14) either at least partially in can be polled individually in a manner known per se, or their chained stations (21; 17, 18) one after the other to respond to the polling signal downstream data stations (13, 14; 19) one after the other. 12. Plant according to one of claims 6 to 11, characterized by a common modem (15) between the transmission channel (*) and thier Chain of data stations (12,21,13,14).