KR920003832B1 - Communication bus interface unit - Google Patents

Abstract

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Description

Communication bus interface device

1 is a block diagram of a station computer network in a conventional configuration incorporating a bus interface device according to the present invention.

2 is a schematic partial block diagram showing the connection of two bus interface devices to a transmitting bus and a receiving bus of a branch computer network;

3 is a schematic block diagram of a logic switching arrangement that is keyed to the operation of the bus interface device of the present invention.

4 is a diagram showing the format of a data packet used for transmission of data and control messages in a branch network.

5a-5c illustrate logical connections made in a connection table of a generating station and a receiving station bus interface device for the data mode, talk mode and remote mode, respectively.

6 is a block diagram of a schematic hardware device for a bus interface device of the present invention.

FIG. 7 is a detailed block diagram of a portion of the bus interface device of FIG. 6 showing the relationship between synchronous data link control (SDLC) and other hardware components.

8a-8c or a flowchart that orders the functions performed by a bus interface device in response to a CALL command, a PCALL command, and a REMOTE command.

9A and 9B are flowcharts for ordering functions performed by the bus interface device in response to a TALK command.

10 is a flowchart that orders the functions performed by bus interface autonomy in response to an Ann command and a MESS command.

11 is a flowchart for a task exchange program employed in a bus interface device to divide processing time among a number of tasks to be executed together.

12 is a state diagram illustrating the operation of a bus interface device in transmitting a message using a regular autoselection protocol.

13 is a state diagram illustrating the operation of a bus interface device for sending an acknowledgment message immediately.

14 is a state diagram illustrating the operation of a bus interface device in receiving a connection request message and a disconnection request message.

15 is a state diagram illustrating the operation of a bus interface device in processing the various steps of the CALL command sequence.

16 is a state diagram illustrating the operation of a bus interface device in handling the receipt of data messages.

Fig. 17 is a state diagram illustrating the operation of the bus interface device in handling the transmission of data messages.

* Explanation of symbols for main parts of the drawings

20: user terminal 22: bus

24: bus interface device 26: computer

28 magnetic disk drive 30 magnetic tape drive

32: high speed printer 34: communication line

40: CPU logic 42: I / O logic

44: DMA logic 46: SDLC logic

54: system data bus 6: system address bus

58: system control bus 60, 62: serial I / O port

76: FIFO circuit 78: bidirectional bus driver

79 local data bus 80 discrete logic element array

82: DMA control logic 84: data transfer control logic

86: bus randomization logic 88: packet end detection logic

90: I / O decryption logic 92: control line

100: switch logic 110, 112: command translator module

114, 116: auxiliary buffer

FIELD OF THE INVENTION The present invention relates generally to locla-area computer circuitry, and more particularly to an interface device for connecting between a communication bus and a number of certain devices, such as computers, displays and keyboard terminals and printers. As computers become cheaper and more numerous, there is a growing demand for simple technologies that enable the interconnection of computer peripherals such as computers terminals and printers. When connected to a network, relatively inexpensive desk-top computers can make calls to large computers and high-speed printers and mass memory devices.

Another advantage of computer circuitry is that the user of the interconnected devices can communicate with each other by what is called e-mail. In a typical electronic mail system, a "host" computer accepts and temporarily stores messages sent from one user to another. The message may be immediately directed to the destination or may be preserved until the intended recipient connects with the host computer and "picks up" the e-mail. In any case, the host computer needs to act as a "post office" in most of this type of mail system.

Of course, the computers may be interconnected via telephone lines using a relatively simple side, demodulator (modem) for connecting each computer or terminal to the telephone circuit. In addition, at least one device in such a network, usually a host computer, must provide "intelligence" to direct the communication phase between the connected devices. However, the present invention belongs to another type of network called the station network, where connected devices usually lie in a relatively small geographical area. For example, multiple offices in a company may have multiple terminals, computers, and other devices connected to a single station network. This allows all network users to share the same database, make calls to the same computer program, and communicate with each other in everyday life. More specifically, the user calls the same word-processing program and dex file, uses a common purge recorder, generates and distributes an internal memoranda and reports it over the network.

Various branch office networks have been developed recently, which employ different network topologies and different communication protocols. The present invention particularly belongs to a network in which each connectable device or "mode" has a single bus phase connected via a bus interface device. Calls to the communication bus can be specified in several different ways, one of which is to allocate time to each connection node in some uniform time division multiplexing (multi-transmission) manner. A more conventional method is to transfer over the bus when any node is ready to run, but to provide some means to detect whether other transmissions are occurring. The latter is often referred to as carrier-sence multiple calling system. Although the present invention is implemented in a system employing this latter method, the principles of the present invention can be applied to systems that will employ other ways to control bus calls.

Using a bus interface device between the network element and the communication bus is nothing new. Georgian. United States Patent No. 4,161,786, issued to George T. Hopkins et al, describes a digital bus communication system in which bus interface devices are connected between a bus and a "subscriber device." Bus interface devices in Hopkins systems have been shown to be partially used to participate in control over bus calls.

Broadly speaking, the function of the bus interface device of the station network is to modulate and demodulate the message, to form a message for transmission to some extent, and to detect and decrypt the received message. Although many branch office networks are utilized today, it is not easy to establish a communication link from a terminal to a computer on the network. Furthermore, a certain amount of computational power, due to the nature of the system overhead in the host computer or intelligent terminal, requires the installation and maintenance of the link.

The communication between the opposite "dumb" terminals is usually done through the host computer and is not in a convenient conversation mode.

Ideally, a bus interface device for use in the branch network should provide the user with as "transparent" bus as possible. In other words, each user should be able to communicate with other user terminals on a computer, device, or network, regardless of the nature of the bus, the message format used, or the location or address of the destined destination. Moreover, the bus interface should ideally be small in size and inexpensive, unlike most devices that have been used for similar purposes. The present invention fulfills this ideal need.

The present invention relates to a bus interface device for use in connecting one or more digital devices to a branch computer network. Among the novel features of the present invention, the most important point is the ability to cooperate with other bus interface devices connected to the network and to establish a real communication link between the two devices, so that no other device is connected until the actual link is broken. It cannot communicate with one of the devices. In addition to other devices, the device originating from the actual link suggests that it only needs to be related to the other device by a given name, which has no relation to the device's address or identification.

Generally speaking, the bus interface device of the present invention is for use in a branch office computer network having a communication bus and a plurality of user terminals connected to transmit and receive information via a bus. The bus interface device of the present invention connects the device to a plurality of user devices capable of sending information to or receiving information from the device, and connecting the bus interface device to the communication bus via a plurality of logical ports. Means for doing so are provided. More importantly, the bus interface device of the present invention has a command mode in which information from a user device is not passed to the bus and information from the user device is passed through the corresponding logic port to the bus and through the same logical port. And logic switching means for each user device that can switch between the information received from the connection mode and the connection mode passed to the user device.

More specifically, the bus interface device includes means for processing a command received from each user device, and the name of the bus interface device called when the bus interface device functions as a calling device for all other bus interfaces in the network. Means for use in transmitting to the apparatus and means for transmitting a connection request to the called bus interface apparatus simultaneously with receiving a called bus interface having a command matching the transmitted name. The logic switching means then switches to the connected mode in response to receiving the connection request confirmation message from the called bus interface device, so that the calling device and the called device are logically connected for the transmission of further data messages.

From the receiving station's point of view of the call, the bus interface device is provided with means for sending a confirmation message if the received name matches the name of the device, and a connection request confirmation if the port is utilized to connect to the calling device. Means for transmitting the message. If a connection can be made, the logic switching means in the bus interface device of the receiving station is switched to the connection or data mode to complete the logical connection between the calling device and the called device.

Once the logical link is completed as described above, another novel feature of the interface device is that the calling device may establish a two-way conversational connection between the linked devices, so that the logical switching means of the calling device is known as the conversation mode. You will be in mode. In the discourse mode, information entered into the calling device is automatically sent to the called device whenever the selected symbol encounters incoming information, and information entered into the called device is encountered whenever the selected symbol encounters incoming information. Likewise, it is automatically sent to the called device. More specifically, the interface device in the case of being used as a generating device includes first storage means for temporarily storing information introduced to the calling device, and second storage means for temporarily storing information introduced to the called device. It is provided. In addition, the apparatus further includes means for transmitting the contents of the first storage means to the called apparatus in response to the detection of the selected symbol of the stored information, and for transmitting the contents of the second storage means to the calling apparatus at the same time. .

According to another feature of the invention, the logic switching means of the bus interface device can be switched to a remote mode command, in which the local device is connected to another bus interface via the bus and then remote commanded to perform a number of selected functions. Will receive. In this way the bus interface device is completely unmonitored from the other station. In the remote mode, the bus interface device may be instructed to leave a message to the remote user. For this purpose, each bus interface has storage means for storing a message that can be received from another interface device operating in remote mode, and a visual indicator that is automatically activated when the storage means contains the message. Each bus interface device also has means for retrieving messages from the storage means. In one mode of operation, the message retrieval means can only operate after the introduction of a particular pass word, so that the personal message beam can be guaranteed.

In view of the novel method, the present invention in the sense of the best light includes the step of completing a communication link between the calling device and the called device by switching the logic switching means of each bus interface device to the connected mode. More specifically, the step of completing the communication link includes transmitting a broadcast message including a designated name of the bus interface device called from the generating station bus interface device, and allowing the receiving station bus interface device from the receiving station bus interface device; Sending a confirmation message indicating that it can be utilized to connect to a possible device; sending a message requesting that a logical connection be made from the generating device; and confirming the connection request from the receiving station device if a logical connection is made. Sending a message, and switching the logical switching means into each connected mode indicating that the communication link is complete. According to another feature of the invention, this message exchange is made without interrupting control of the communication bus for any other user requesting a call.

As mentioned above, the interactive "talk" mode is also an important feature of the present invention. When this mode is required by the generating station apparatus, the logical connection is completed as described above, followed by the step of switching the logic switching means in the generating station apparatus to the discourse mode, which flows into the calling apparatus. The information is echoed back to the device one symbol at a time, but may be sent to the called device whenever it encounters a particular symbol, such as a carriage return. Information introduced to the called device is sent to the originating station bus interface device, where the information is redirected back to the called device and one line to the calling device whenever a particular symbol is encountered. In this way, everything that enters the calling device is observed line by line on the called device, and vice versa.

In operating the bus interface device remotely, the method steps include switching the originating station bus interface device to remote mode and injecting additional commands at the originating station to be executed by the remote device. It functions in the same way as executing commands imported through one. One of the remotely imported commands will be a message command. While receiving a message command, the device stores the message accompanying the storage area and activates the indicator to notify the user that a message has been entered. The user will retrieve some stored message by calling the bus interface device with an "observe" command. If a message was sent using a command that ensures confidentiality, the observe command must be run by an "open" command, while at the same time supplying the user with the correct pass word for the call to the message. An open message is called a notification and will be called without a pass word.

It will be appreciated from the foregoing that the present invention represents a significant advance in the field of local computer network. In particular, the present invention provides for logical connection of two user devices, or user devices and computers, in such a way that the link connection is completed without the physical address or physical identification of the called device and remains uninterrupted until the link connection is interrupted. Provide new technology. In addition, the present invention enables the completion of an interactive discourse mode between two user devices without the involvement of a host computer to monitor or relay messages. Finally, the bus interface device of the present invention will be called and operated remotely for the storage or non-monitoring operation of messages for users temporarily absent from the device station. These and other features and advantages of the present invention will become apparent from the following detailed description with reference to the accompanying drawings.

As illustrated in the figures, the present invention mainly relates to improvements in the field of branch computer network. In particular, the present invention relates to improvements and simplicity in terms of how a user device is interconnected to a network from a user's point of view, and an improvement in the form of communication mode useful to a user without the assistance of a host computer connected to the network. .

[Description of local-area network]

1 and 2 show the periphery of the network, where the invention works advantageously. As shown in FIG. 1, a typical network has a plurality of user terminals, denoted by reference numeral 20, which are usually a relatively small geographic area, such as one building or group occupied by a single company or corporation. In several places in the building. The communication link connecting the terminals is a bus 22 to which each terminal 20 is connected via a plurality of bus interface devices 24. In fact, each bus interface device (hereinafter abbreviated as BIU) is connected to the outgoing bus 22a and the receiving bus 22b, but as shown in FIG. 2, the outgoing bus and the receiving buses have an amplifier. It is joined at the head end of the so-called bus.

Bus 22 takes a variety of forms but in the preferred embodiment of the present invention the bus is a wideband coaxial cable and the messages are transmitted in the form of amplitude modulated radio frequency carrier signals. This choice offers the advantage of enabling the use of standard, relatively inexpensive cable television technology for many bus equipment. In addition, because only a portion of the cable bandwidth is used for digital communication, the cable may be used for other purposes in certain applications. For example, closed-loop television signals can also be transmitted across networks between remote end stations.

It is also connected to the bus 22 between mainframe computers 26 in a typical configuration, where one or more BIUs 24 are used to connect to the bus to make computer calls for multiple concurrent call users. The computer 26 will of course be connected to useful peripherals such as the magnetic disk driver 28, the magnetic tape driver 30, and the high speed printer 32. Computer 26 may also be connected to a communication line labeled 34 to exchange information with a computer at a remote location. Some of the user stations may have printers 36 useful for them, although it is usually uneconomical to impart printing capability to all stations.

In various applications, the computer 26 acts as a "host" for the genetic terminal 20, some of which connect to the computer to control the execution of the program or to call large databases in the computer. In some systems, computer 26 acts as a host for the collection and distribution of "e-mail" for all forms of user-to-user communication. In this general type of conventional network, communication with other devices on the network is accomplished by a call sequence in which the destination device must be addressed by some form of hi-ware identifier, which is often on each bus 24. Is related to the setting of the switch.

In order to reduce complexity or cost, each BIU of the prior network of the present invention is coupled to only one user device. As shown in FIG. 2, each BIU 24 of the present invention is connected to one or more user devices, indicated by reference numeral 38. 1 shows that one of the devices is one of the printers 36, which can be called independently from the other device. In the case of the embodiments described herein, two devices 38 may be connected to each BIU 24, but the BIU is designed to easily expand the number of user devices per BIU.

According to one important feature of the invention, each BIU 24 in the network is addressed with a single name that the user can easily change. As will be described in detail later, the communication link is established by a simple means of typing commands such as CALL, SMITH, BILL at the user terminal. The data is then sent to the terminal of Bill Smith. The connection with the computer can be made by keying a command such as CALL COMPUTER A. The conversation mode established by keying commands like TALK SMITH, BILL is much more powerful. In this mode of operation, everything that is keyed in one of the linked terminals appears on the screen of the other, and the conversation takes place without the introduction of additional commands. Note that talk mode functions without the assistance of the host computer. It is purely user-to-user communication mode.

Another novel feature of the invention is a command that allows a user to control an unmonitored device at a remote location from his terminal. When a command REMOTE comes in with the name of another user device, the BIU of that device becomes controllable by the user giving the REMOTE command. In addition to this feature, the user can, for example, connect a remote non-monitoring terminal with a printer at a third location.

Another novel feature of the present invention is that it leaves a message at another user location, i.e. a secret message or a non-secret "publish" message, and does not use a host computer for this type of e-mail.

The above and other features of the present invention will be described in more detail below. However, some preliminary explanation of the hardware configuration of each BIU 24 is needed.

[Hardware Configuration]

As shown in FIG. 6, the main components of the BIU 24 are the central processing unit (CPU) logic 40, the input / output (I / O) logic 42, the direct memory call (DMA) logic 44 ), Synchronous data link control (SDLC) logic 46, random-access memory (RAM) 48, read only memory (ROM) 50, and electrically erasable programmable read only memory (EEPROM) (52). These logic modules communicate with each other via a system data bus 54, a system address bus 56, and a system control bus 58.

The CPU logic 40 is a typical Digian and has a Z 80 A CPU (Xylolog 4 MHz 8-bit microprocessor) and a standard Xylolog counter / timer circuit (CTC). I / O logic 42 has a standard Xylolog Z 80 A dual synchronous receiver / transmitter (DART) chip, which is coupled to two serial I / O ports, denoted (60) and (62).

The DMA logic 44 includes a Zlog A 80 A DMA control chip, which transfers all data between the memory and the SDLC logic 46 regardless of the CPU logic 40. The SDLC logic performs the transfer of data to or from the communication bus 22 and also has other control logic to be described in more detail with reference to FIG. The memory device is conventional, including a RAM 40, which in the illustrated embodiment has 6,144 bytes (6K) of memory consisting of three RMA circuits with part number M 58725.

ROM 42 has a memory of 12K bytes consisting of three circuits with part number 2732A. Finally, the EEPROM 52 is composed of 2K bytes (part number 2815) and is used to store information that can be changed when the power is turned off but is not lost. For example, the BIU name and location are stored in the EEPROM using the EEPROM write control logic 64. Of course, the ROM 50 contains the program and control logic necessary to perform the BIU function as will be described while the RAM 50 is used for temporary data storage.

The modem (modulator / demodulator) is not shown in FIG. 6 but is connected to SDLC logic 46 via line 66. The modem transmits a message packet via the communication bus 22 by amplitude-modulating the radio frequency carrier signal, and receives the message packet by demodulating the received carrier wave. In addition, SDLC logic 46 also performs some control via DMA logic 44 as indicated by line 72.

7 illustrates the SDLC logic in more detail, including a standard SDLC chip 74 (part number WD 1933 B-02, manufactured by Western Digital, Inc.), a first-in-first-out chip 76 ( Xylolog 128-byte FIO chip, part number Z 3038) and a bidirectional bus driver 78 (part number 74 LS 245) connected between the system data bus 54 and the local data bus 79. In essence, since the FIFO circuit 76 inserted between the local data bus 79 and the system data bus 54 acts as a buffer mechanism between the SDLC chip and the DMA chip, these two circuits can operate asynchronously. SDLC logic 46 also has an array of discrete logic elements, denoted by reference numeral 80, which in turn is DMA control logic 82, data transfer control logic 84, bus arbitrary assignment logic 86 A packet end detection logic 88 and an I / O decryption logic 90 are provided. The bus arbitrary designation logic 86 controls not only the use of the local data bus 79 but also the data transfer direction in the bus driver 78 as indicated by the control line 92.

The data flow between the SDLC chip 74 and the FIFO chip 74 is controlled by the bus randomization logic 86 and the data transfer control logic 84 and via the DMA logic 44 and the system data bus 54. The data flow between the FIFO chip and RAM 48 is partially controlled by data transfer logic. The CPU logic 40 sends control information to the SDLC chip 74 via the bus driver 78 and the local data bus 79, and the state information from the SDLC chip again controls the bus arbitrary designation logic 84. Can be sent to the CPU logic via the reverse path.

In addition to the above functions, the local bus 79 is used to transmit CPU control information to the system control I / O port 93. It is used to generate various I / O control signals to audible and visible indicators on the EEPROM 64 and bus interface devices.

The bus randomization logic 86 and the packet end detection logic 88 communicate with the CPU logic 40 via the CPU wait line 94 and the CPU non maskable interrupt line 96, the latter being the SDLC. It is used to notify the CPU logic of the transfer of outgoing data through the chip 74 or the completion of the incoming data transfer from the SDLC chip to the memory.

The I / O decryption logic receives address and control information from the system address bus 56 and the system control bus 58 and supplies I / O control signals on the line 98 used to control various input and output operations. do. The entire discrete logic array 80 is configured in the form of three logic array chips, two of which are part number PAL 1018 and the other part number PAL 16 R 6.

Although the detailed logic design of the hardware elements shown in FIGS. 6 and 7 is of critical importance to the invention as claimed, other design methods may be used to couple the BIU to the communication bus 22 and the local port. have. However, a complete schematic of the complete hardware is included in Appendix I of this specification.

[Overview of Arithmetic Mode]

The BIU of the present invention provides each user with a convenient interaction technique for communicating with other users or computers connected to the network. The default or default mode of the BIU is command mode. It should be noted throughout the description that the word "mode" or "state" is not necessarily added to the BIU except for the logic of the BIU, which deals with the particular device connected to the BIU. For example, the BIU may be in command mode for device # 1 and command mode for device # 2.

In command mode, the BIU receives and translates information that has entered the user device and checks to determine which of the information includes one of a list of valid commands. In this mode, the user communicates with his local BIU but not with the communication bus 22. When a command is recognized by the BIU, it takes appropriate action to match the command. Some of the commands are simply requests for status information that can be supplied immediately to the user terminal. For example, the status command STAT on gives the user the current status of the BIU to which his device is connected. Other commands are used to modify various parameters related to the BIU. For example, the NAME command is used to name or modify a user's name, and the LOCATION command is used to enter or modify a user's location. After some preceding command, the action required by the BIU is performed and control is returned to the user in command mode.

However, the mainly related instruction of the present invention is to put the BIU in another operation mode. Three other modes of interest are data mode, talk mode, and remote mode. In data mode, a local user device is logically connected to another device, usually a computer, but in some cases to another user device. In the data mode, the logical connection is initiated by the originating device, and information sequentially entering or exiting the originating device is treated as data to be sent to the device on which the logical connection is made. The CALL command is used to make an initial connection and make a transition to data mode.

According to an important feature of the invention, only the parameters required for the CALL instruction are the designated names of the intended destination BIUs. Each BIU in the network actually has four names, including the best and last command, the station name, and the BIU name, which is the serial number of the device. The CALL command uses two of four names, typically the best and last names. In the case of a user terminal, for convenience, the best and last names may be selected to be the best and last names of the users themselves. In the case of a computer, the name may be a well-known computer name identifying the computer, such as VAY, IBM, and the like.

In the discourse mode, the logical connection is made as in the case of the CALL command, and there is an additional modification to the BIU logic to form an interactive link with the called device, which is usually another user terminal. In the discourse mode, the information introduced by the calling user is automatically displayed on the called user terminal, and the information introduced by the called user is automatically displayed on the calling user terminal. In this way, two-way conversations can be performed without any host computer intervention.

In the remote mode introduced by giving the REMOTE command, the user can call the remote BIU as he or she is. When used in conjunction with the CALL command, REMOTE allows one user to interconnect two devices at a second and third location that is not monitored. When used in conjunction with remote mode, a message command (MESS) allows a user to memorize a message from a remote BIU for later observation by a user at a remote location. Calls to messages can be made by using only the OPEN command, which requires the introduction of a user password, followed by a VIEW command and terminated by a CLOS command.

How these functions are performed is described in the following description. The functionality of the BIU can be discussed at a number of different computational levels. In essence, it is the CPU logic 40 that controls various functions under the control of a series of command programs stored in the ROM 50. A list of these programs is shown in Appendix II. However, it should be understood that programming is complex because the CPU must perform multiple functions such as input and output at substantially the same time. For this reason, a program is organized into a number of separate tasks that share a CPU under the control of a task exchange program that rapidly switches from one task to another. Further complicating the programming is a number of program segments that are executed in response to interrupt signals provided to the CPU logic, for example, to indicate that data packets have been delivered on or off the bus. Since the programming task is not used as a convenient tool for the description of the present invention, it will be described later.

The operation of a program embodying the present invention will be described at a functional sequential level rather than focusing on specific program code. Each main command will be described with reference to a flowchart of the sequence of related functions and a logical table coordinated by the program.

The operation of the BIU will also be described using a logical state diagram that is useful in observing the impact on each BIU during the various stages of the instruction sequence.

Logical table organization is coordinated by the program to maintain and disconnect these connections sequentially while completing the desired connections between devices, logical bus ports, and processing tasks. Understanding this combination of tables at least from a logical point of view is essential to understanding the functionality of the CALL, TALK, and REMOTE commands, and the combination of these and other commands. Logical table organization is schematically illustrated in FIG. 3 as including a symbolic orientation table, denoted CODTAB, a packet orientation table, denoted PODTAB, and optionally switchable logic, denoted 100. The organization of the logical tables will not be explained in detail, so use the list in Appendix II. However, it can be said that the two logic tables and the switch logic 100 together form several data paths through the BIU.

Entries # 9 and # 10 of CODTAB, referred to as COD-9 and COD-10, respectively, are logically connected to two I / O ports 102 and 104 for two local devices. In the case of the command mode, only the link connection provided by the switching logic 100 is the command mode link indicated by dashed lines 106 (108). Link 106 connects COD-9 to COD-1 and link 108 connects COD-10 to COD-2. The command translator module 110 having an associated key board buffer is logically connected to COD-1. Each link 106, 108, and in fact each other link described with respect to switch logic, may be thought of as a bidirectional data path. Thus, when the user of device 1 sends out a symbol of information via the port local I / O 102, each symbol is sent to the command translator 110 via the link 106. One function of the translator is to initiate transmitting "echo" back each received symbol to its source. As a result, the user will be able to see his incoming symbols displayed on the screen of his terminal. The translator 110 stores the received symbol in the key board buffer and simultaneously translates the received information and takes appropriate measures when the information constitutes a command.

In essence, information or data is not moved at all in performing data transfer in a logical table over the same line as the link 106. Rather, the indicators in the logical table are modified to reflect the apparent movement of the data.

The other command translator 112 performs the same function as the other translator 110 if there is no reception at the device 2 in connection with the COD-2 via the link 108 from the port 104. In fact, the two command translators 110 and 112 are configured in the form of a single program. However, the program is designed to be a "re-entrant" meaning to be called or imported from one or more calling programs without waiting for the completion of a previous call. This shows that copying multiple identical programs is useful. The two auxiliary buffers 114, 116 below the command translators 110, 112, indicated by dashed correction lines, are connected to COD-5 and COD-6, respectively. These auxiliary buffers are only used in the TALK instruction as described. In addition, there is an associated buffer logically connected to COD-0 of another command translator 118. This is only used for REMOTE commands.

In the description of the CODTAB and PODTAB tables, only the command mode has been considered, but no connection to the PODTAB has been described. PODTAB also contains a plurality of entries, in which only # 0, # 1, and # 2 are shown. Entries # 1 and # 2 are connected to logical bus ports # 1 and # 2, respectively. Port # 1 is the path through which Device # 1 calls the bus, and Port # 2 is the path through which Device # 2 calls. According to the connection to be described for the various commands, the switch logic 100 can be modified to make a link connection from the CODTAB entry to the PODTAB entry so that the device connects to its output port.

CALL command:

The CALL instruction forms a logical connection between the calling device and the called device. The logical connection is stored in the CODTAB and PODTAB entries of the BIUs at both ends of the connection. However, there is a message exchange between the calling BIU and the calling BIU to locate the called device first and then attempt to connect with it before the table entry is modified to record the connection. Before describing the nature of these messages, it may be useful to switch topics to define the format of the message packet used to transmit data and control messages over the communication bus.

The message packet form is shown in FIG. It contains a destination address that defines a unique BIU and a field (field) for the destination port within the BIU. Some messages will be broadcast to all destinations, in which case the destination addresses will all be zero. The packet also includes fields for the source address and the source point in the source BIU. There are a command field indicating the type of information contained in the packet, a packet length field, and a variable length field for data to be transmitted. Finally, for error checking purposes, there is a field for the cyclic redundancy code and a 2-byte field for the packet end flag.

The various types of information to be included in the packet are given in the following table, where each entry has a unique command code for the entry in the Message Packet Command Code field.

Abbreviation call message form

ACK data check

Wait for WAC Check

Confirm no NAC data

CRA connection-request confirmation

During CAB connection-verification

Determine if a QAA question

Confirmation of NRA naming requirements

DIS disconnected

QBN Name Question

Resume RSM Data

DAT user data packet

CRQ connection request

NRQ nomenclature requirements

QNA Name Question Check

The purpose of each message type will be apparent from the description of the progress of each command, particularly with respect to its state diagram.

The CALL instruction will now be described with reference to the flowcharts of FIGS. 8A-8C. The sequence is introduced as shown at 120. The regular CALL command assumes that the caller does not want to connect to a specific port of the called BIU. Typically, a user will use a CALL to connect with a computer or to connect a user with their BIU. In the case of a computer, the user cannot select which ports will be used to call the computer. A variant of the CALL instruction is shown as PCALL (123), which requires the caller to specify which port to connect to. This would be used, for example, if the user wishes to connect his terminal to a printer located at a remote end station and connected to the bus via a particular BIU port. Either way, in the case of normal CALL, the parameter is set to select any port as shown in block 122, and in the case of PCALL the parameter is set to select a particular port as indicated at 124. The REMOTE instruction indicated at (125) is a variant of CALL, and at this time, the parameter may be set for selection of port # 0 as indicated at (126). The effect of the REMOTE command is described in more detail below.

Each form of the CALL instruction requires a connection to be performed, as indicated in block 128, which is extended in section 8b and named SYMCOM is a subroutine. If a successful connection is made, after a return from SYMCOM indicated by an affirmative response to the question made at block 130, a successful return is made from the call sequence as indicated at 132. If the connection is unsuccessful, a message indicating that the remote BIU is in operation is displayed to the caller as indicated at 134 and an error return is made as indicated at 136.

The connection process is shown in more detail in FIG. 8B, which first asks at block 138 whether the PODTAB entry will be connected to the port for the bus and then at 140 the BIU that matches the name given as a parameter in the CALL command. Enter a subroutine called GETNMS to get its name. GETNMS is shown in detail in FIG. 8C. The sequence first enters a table area for receipt of a response at block 142, and then enters a query step for a name (block 144), constructs a question message packet for a name (block 146). , Sending the packet (block 148), placing some response in the assigned table (block 150), and then returning the calling BIU to the dormant state before returning to the calling program.

Returning to the SYMCOM subroutan, a check is made to determine which response will be received as a question message for the name (block 154). If nothing is received, an error return path is taken, but if there is any valid response The first one is recovered for further processing (block 156). Up to this point, the calling BIU has sent a Question of Name (QBN) message to all other BIUs on the network and also received one or more responses from the BIU whose name matches that specified in the CALL command. If several BIUs are connected to a single computer, they will be assigned the same name, resulting in a situation where there may be multiple responses to QBN messages. The calling BIU preserves the source address of all QNA (Name Question Acknowledgment) responses and immediately sends a QAA (Question Acknowledgment) in each case.

In decision block 158 of FIG. 8B, it is determined whether a connection to a particular port is required. If necessary, the PCALL or REMOTE command is instructed to attempt to connect to the required port (block 160), and if successful (block 162) a successful return from the SYMCOM subroutine is made. Attempts to connect to the port at block 162 basically include sending a Connection Request (CRQ) message to the remote BIU to determine whether a connection to another BIU has already been made. You need to check the field. The remote BIU sends a connection request confirmation message if the port is available, or a CAB message if the port is unavailable. If the required port is operating as determined at block 162 or if no free port is available for the CALL instruction as determined at block 164, the next entry in the table of successful names is retrieved (block 166). Control is passed back to block 158 to complete the connection. If there are no more entries in the table (block 168), a return is made to indicate that all ports are in operation as indicated at 170.

In processing a CALL instruction at block 164, if a port is available, a connection to it is attempted (block 172), and as indicated at block 176 if successful as determined at block 174. Successful return is made. Otherwise, a search is made for another port on the same BIU, and control is passed back to block 172 to attempt another connection. If all ports have been attempted (block 180), control is passed to block 166 to find another BIU table entry.

An important part of the CALL command sequence occurs when a successful connection is made to a remote BIU. At this point, the CODTAB and PODTAB entries at both stations of the issuing station BIU and the receiving station BIU are varied to complete the logical connection between the called device and the calling device. This is shown for CALL in FIG. 5A. In the producing station BIU, a connection is made between COD-9 and COD-1 indicating that device # 1 is logically connected to its bus port # 1. The BIU address and the port number of the CALL recipient station are contained in the POD-1 entry. This is a POD to POD entry in the table as indicated by the broken line between POD-1 of the originating station BIU and POD-2 of the receiving station BIU. It is assumed that a connection is made to the second port of the recipient station BIU because there is a PCALL instruction that defines that port only by way of example, or because it is the only available port.

Note that the command mode of COD-9 and COD-1 is not already present in Figure 5a after CALL. Data entering device # 1 of the originating station BIU will be delivered to device # 2 of the receiving station BIU via the completed call link connection. Protocols for data transfer are described below in connection with the 16th and 17th degrees.

[Call command and mode:]

Since the CALL instruction and the sequence of actions it initiates have been described, the capabilities of the discourse instruction can be better understood. As shown in the flow charts of 9a and 9b, the TALK instruction sequence begins by initiating a normal CALL instruction, as indicated at 190. Next, there are two calls to the subroutine name ATTACH at 192 and 194. The first ATTACH call at 192 has the effect of removing the CALL connection made at the originating station BIU and making another connection. In the example of FIG. 5, the CALL connection between COD-9 and POD-1 is first removed and a new connection is made between COD-9 and COD-1. It should be recalled that this is the common mode link shown in Figure 3 and that COD-1 has a command translator and keyboard buffer associated with it. The next ATTACH call at 194 has the effect of making a connection between POD-1 and COD-5, which has a secondary buffer 114 with command translator 110 associated therewith. After both buffers are initialized in block 196, the symbols entering the buffer are checked one by one and echoed back to their respective source devices. For example, a symbol from a local device is placed in a keyboard buffer and echoed back to the local device via a COD-1 to COD-9 link. Likewise, the symbol from the remote device reaches the auxiliary buffer via the POD-1 to COD-5 link and echoes back to the remote device via the same link. The connection at the receiving station BIU is the same as for CALL in the case of TALK.

The operation of the command translator 110 operating in the discourse mode is shown in the remaining flowchart of FIG. 8A. The per symbol check is performed by a call to the subroutine name DOCOD at blocks 198 and 200. If a carriage return symbol is detected in the keyboard buffer (block 202), then a call to another subroutine (PRTBUF) is made at block 204, the function of which subroutine is to replace the entire buffer with another device, That is, to a remote device. This function is performed by readjusting the table entries and indicators. In practice, the information line of the key board buffer is passed by the command translator 110 to the COD-5 entry point for the table, then passes through the already completed link from COD-5 to POD-1 to reach the remote device. .

Similarly, when a carriage return symbol is detected in the auxiliary buffer (block 206), a call to PRTBUF (block 28) is made to connect the entire line of the buffer to the local device. In this case, the information in the auxiliary buffer 114 is passed to COD-1 to pass through the link and local device completed in COD-9. So far, once the TALK connection is established, the local user of the originating station BIU will notice that he has "talked" to the remote user device by simply kinging in the message. After every carriage return, the line of message will be sent to the remote device. In a similar way, each line into which the remote user enters appears in the local device.

Figure 9b illustrates in detail the DOCOD subroutine used to process symbols in the buffer in discourse mode. In the first decision block 210, a check is made to determine whether to return to the common mode. If returned, the common mode connection is resumed (block 212) and an appropriate return is made as indicated at 214. If not, the appropriate COD entry is checked for the presence of another symbol (block 216), and a return to the calling program is made if there are no symbols to be processed. If there is a climate to be processed, it is determined at block 218 whether it is a control symbol. If it is a controller call and it is a carriage return (block 220), the carriage return and line feed are echoed back to the source of the symbol (block 222) and the carriage return flag is set for use by the calling program. If the controller call is not a carriage return symbol, it is processed before returning to the calling program (block 224). If the symbol is a printable symbol, it is echoed back to its source device before returning to the calling program (block 228).

[REMOTE command and mode]

As mentioned above, the REMOTE command is treated as a variant of the CALL command sequence, except that the REMOTE command specifies a connection to port # 0 at the recipient station BIU. The main part of this connection will be apparent from Figure 5c. The originating station connection is the same as for CALL, ie the connection from COD-9 to POD-1 in the example. It will be recalled that the recipient station BIU makes a connection from POD-0 to COD-0, with other command translators and buffers associated with the COD-0 entries in the table. After issuing a successful REMOTE command, the originating station user terminal will still appear to be in common mode. Everything introduced into the terminal will be directed back by the receiving station BIU, not by the originating station BIU. The user of the originating station will be effectively controlled by the remote BIU on their behalf and will issue any normal commands to be executed by the remote BIU.

Perhaps the most dominant feature of the REMOTE command is that it allows the user to connect to two different devices on two remote stations and an unmonitored station. For example, suppose a high speed printer is connected to BIU port # 2 named BILLSMITH and one terminal is connected to BIU port # 1 named JAKEJONES. Another user of the BIU can use the following command sequence: REMOTE JONES, JAKE PCALL SMITH, BILL, 1, 2 (from terminal on port # 1 of Jones BIU to printer on port # 2 of Smith BIU) Terminal) can be connected to the printer.

[Message and Announcement Commands]

This command can be issued in remote mode, in which case its effect is to memorize messages in the remote BIU. This command can also be issued in command mode. For example, a user may leave a notice on his bus interface device to explain his absence to another user. The only difference between the two commands is that the announcement (ANN) is not secret and can be observed by anyone calling the BIU to which the message is directed. On the other hand, the message command (MESS) can be observed only by a person who knows the special BIU pass word. Appropriate flags are set in block 230 and 232 of FIG. 10 to indicate what type of command (ANN or MESS) is to be performed. In this respect, the functions performed in executing the two commands are the same. The privileged flag set or not set at blocks 230 and 232 will not be considered until a VIEW command is attempted to observe the stored message. If the message is secret, an OPEN command will be needed to provide a pass word.

Message Sequence The next step is to temporarily suspend the call to the system message buffer when this message is being stored (block 234) and find a free message block (block 236). If no message block is found (block 238). The system message buffer is restored (block 240) and a return to the calling program is made. If a free message block is found in block 238, the block is tagged in use (block 242), and the block indicator is initialized (block 244); The contents of the keyboard buffer are passed to the message block at block 246. The block that was in use is then set as available, a beep ton is turned on to indicate the memorized message (block 250), the light is turned on for the same purpose (block 252), and the system The buffer is restored before returning to the calling program (block 254).

Task configuration

The foregoing functions have been described in terms of the order of operations performed by the BIU. Indeed, various functions are performed by, or at least initiated by, a number of separate program modules called tasks. The transition from task to task is controlled by a program called SWAP, the flowchart of which is shown in FIG. Each task makes a call to SWAP very frequently and on each entry to the SWAP program the calling task is suspended and another task resumed. The SWAP will be described first for the operation of the hard round-robins in a sequential order and then various tasks will be identified.

At the entry of the SWAP program, the register of the calling task is first preserved as indicated by block 260 and then the watchdog timer is reset at block 262. Position dog timers are devices typically used in real-time computer systems to ensure that certain keys are performed at a suitable time. The timer also generates an interrupt signal if it is not reset within a predetermined time period, which can be used to reinitialize the entire system if necessary. Because SWAP programs are thought to be frequent, the failure of a SWAP call means only some form of malfunction that requires a recovery method to be taken. Another important function performed by the SWAP program is to service CODTAB and CODTAB entries. At decision block 264 it is determined whether it is time to service the CODTAB entry. This decision is based on checking memory locations to see if it is zero or not. The interrupt service routine is used to set the memory location to a nonzero value at a rate of 160HZ. When a non-zero value is detected at block 264, a branch to a rutin called TIMEDX shown in block 266 is made, which is essential for the service of the CODTB entry. In this embodiment of the present invention, there are a total of 16 entries in CODTAB, although not all are used. At each entry to TIMEDX, one entry of CODTAB is checked to see what action is needed, and the memory location checked at block 264 is reset to zero. Thus, the total CODTAB is served at a rate of 10 HZ.

SWAP programs are estimated to flow at a rate of thousands per second. If a branch is not chosen as a TIMEDX routine, then at all its other entries, another branch is chosen at block 268 as a routine called UNLOAD. Serving a CODTAB entry in a TIMEDX routine involves examining each entry to see if an information packet is delivered over one of the completed COD to COD links or COD to POD links in data mode, conversation mode, or remote mode. Include. In order for the delivery to take place or to be able to do so, a program running under TIMEDX performs the delivery by appropriate adjustment of the cover page. Strictly speaking, it should be recalled that there is no movement of information through table links, only a logical movement of information carried out by varying the indicators that position information in relation to I / O ports and handling tasks related to that table. will be.

In servicing a PODTAB entry, the UNLOAD routine performs a function on PODTAB similar to what TIMEDX routine does for CODTAB. Each PODTAB entry is examined in turn to determine what delivery is to be done and whether it is done at any time if possible.

The rest of the SWAP program is relatively commercial. The knowledge section about the current task stored in the register at block 270 is also preserved, followed by identification of the next task to be introduced at block 272. As already mentioned, this is done in a simple round-robin fashion. If the task can proceed soon (block 274), a new indication for the stack of reserved task registers is obtained (block 276), and the register of the new task is re-memorized (block 278). Control is transferred to the new task by executing a return at 280.

Task # 0 is the initial system initialization task. Its function is to initialize the entire system, including certain variables in RAM and EEPROM. It also initiates the operation of other tasks. When power is first applied to the BIU, or when the BIU is reset to an initial state for some reason, after this initial sub-step, task # 0 becomes a program called CCPTSK. This is an execution task that deals with the various operations required by the system, such as handling updated QBN (question about names) calls for the operation of the visible and audible indicators.

Task # 1 is a central program, designated OUTSDL, that handles outbound SDLC information. Basically it is needed to bus the racket when it reaches the PODTAB entry. Task # 1 is also essential for entering a packet into a BIU for data reception operating in a so-called receiver driving mode. The receiver drive mode will be described with reference to the data mode state diagrams (FIGS. 16 and 17), but in short it simply means that data transfer is under the control of the receiver rather than the transmitter of the data.

Tasks # 4, # 5, and # 6 are all command translator tasks designated as CIL. Task # 4 is used for the recipient station BIU in the REMOTE command in conjunction with entry COD-0 in CODTAB to translate the command from the originating station BIU. Tasks # 5, # 6 are associated with entries COD-1 and COD-2, respectively, and are used to translate commands from the local apparatus as described in connection with various commands.

The task combination area overlay is a number of execution request routines made from the task and a number of interrupt response routines to which control is transferred upon receipt of the interrupt signal from the input / output device. The full statement of this program does not add much to the understanding of the present invention. In particular, it relates to various modes of connection and communication between holding devices. If a more detailed description is needed for the operation of a particular routine or task, see the complete list of all CPU programs in Appendix II.

[BIU State Diagram]

The state diagrams of FIGS. 12-17 are not always directly related to the programs and executable tasks that have been described, but are illustrative representations of the order of dictionaries related to various BIU functions. Each circle in the state diagram represents the state of the BIU, or more precisely, the state of a portion of the BIU as the BIU can assume a different state for another of its attachments. The path drawn between the state circles represents the state change in the direction of the arrow on the path and is caused by a "trigger" event written on the horizontal line that appears when the path is blocked. In most cases the "trigger" event causes a change in state as well as a "action" written below the horizon of the transition path.

Figure 12 illustrates the action of a transmitting BIU in sending a message according to a regular contention protocol. This means that a message packet is sent after a delay of 200 microseconds if the bus is not yet in use at the end of the delay. When a request is received that requires the transmission of a regular auto-select protocol response, the BIU goes to state 1 if the bus is not busy, or to state 2 if the bus is busy. In state 2, the transmission task is temporarily stopped, but will often resume to return to state 0 again until the bus is no longer busy. In state 1, a delay of 206 microseconds is allowed to elapse. Then, if the bus is still not used, a message is sent and the device goes to state zero. However, if the bus is busy at the time the delay is completed, the task will be stopped by the SWAP program call and the BIU will proceed to state 2. If the SWAP program resumes execution of the transfer task, it will return to state 0, at which time it will return to state 1 if the bus is not already busy and wait for a new delay after the transfer.

13 is a corresponding state diagram for an immediate acknowledgment transmission. Whenever a BIU receives a message that requires an immediate response, an appropriate acknowledgment message is constructed and sent immediately. As can be seen, this has the advantage of providing a response to various requests, such as connection requests, without waiting for the necessary time delay in the automatic selection response of the rectification. In making an immediate response, the BIU does not give up the bus until a response is sent. The broadcast signal remains until the immediate response is complete and no other BIU can make a call to the bus.

14 is a state diagram illustrating a BIU in various states in which connection and disconnection requests are received. In state 1, the BIU is in standby and disconnected state. If a correction request CRQ message is received when it is not in use at state 0, a connection request confirmation (CRA) is sent immediately to proceed to state 1 where the BIU is in use and connected. If a connection request (CRQ) is received while in a busy state, an immediate connection confirmation busy (CAB) message is sent. When a DIS message is received, the BIU reverts back to state zero. The same situation arises when a BIU is required to initiate a connectionless connection by sending six consecutive DIS messages.

15 is a state diagram related to the order of CALL commands. When in state 0, the initial state, the BIU receives a CALL command and sends a QBN message; Goes to state 1 and waits for a response. If no response is received within a predetermined time period, the BIU recurses to state 0, but upon receipt of a Named Question Confirmation (QNA), the BIU immediately sends a QAA to determine if it is a question, and proceeds to state 2 to further QAA responses. It is received and treated in the same way. When the time allowed for a response expires, the BIU selects the first response it received and goes to state 3 to attempt to contact the called BIU.

The connection request (CRQ) will be sent up to eight times when in this state 3. If an immediate connection request confirmation (CRA) is received in any operation, the BIU returns to state 0 to report a successful connection. If an immediate CAB busy message is received, the port is set to the critical state and the BIU proceeds to state 5 to select another port. State 7 is reached if no response is received after attempting to connect 8 calls. If another port is available, it returns to state 3 to attempt up to eight additional connection requests. If no other ports are available at all in the first selected BIU, then transition to state 4 where another BIU is selected as the original QBN message from the received response and transition to state 3 to attempt to connect with another BIU. If the BIU is no longer available and a connection is made, finally it transitions back to state 0 with an error indication.

The state diagrams for the PCALL and REMOTE instructions are mostly similar to those in FIG. The only difference is that state 5 does not exist for the command because a particular port is selected for the connection.

16 is a state diagram showing various states of a BIU serving as a receiver in data transmission. This should be considered in connection with the seventeenth diagram showing the corresponding state of the BIU acting as a transmitter in data transmission. State 0 in FIG. 16 shows the receiver in the standby state. If a data packet is received while in this state, it is an immediate acknowledgment (ACK), and this sequence continues normally until all data has been received. This is called the sender driving mode in data transmission.

If the receiver is busy as shown in state 1, the received data packet (DAT) immediately generates a wait acknowledgment (WAC) transmission and the receiver proceeds to state 2 indicating that the transmission is in progress. If additional DAT messages are received while in this state, additional WAC messages will be sent in response immediately. If the receiver is not in operation, it sends a data resume (RSM) message and proceeds to state 3, waiting for data transmission. If there is no more data, a No Data Acknowledgment (NAD) message will be received and the BIU will return to state 0. If a DAT message is received, the receiver responds with an ACK and returns to state 2. At this point, no additional data will be accepted until another RSM message is sent. This is called data transmission mode of receiver operation. Of course, BIU won't stay in state 3. It will send 10 RSN messages, and if no additional data or data acknowledgment (NAD) is received, it will send a DIS connection message six times and proceed to the disconnected state shown as state 4. In a disconnected state, additional data messages will be ignored and no further data transfer can occur until the connection is reestablished.

From a transmitter perspective, FIG. 17 illustrates initial state 0, which first receives a request for the BIU to send data. It sends a DAT packet and waits in state 1 for confirmation. If an ACK message is received, the transmitter returns to state 0 and waits to send more data. This is the emitter drive mode. If no ACK is received after the termination period, the DAT message is retransmitted and this sequence is repeated up to 10 times before proceeding to the disconnected state. If while in state 1, a WAC response is received, the transmitter goes to state 2, where the transmitter waits for an RSM message from the receiver. It is now back in receiver drive mode. When an RSM message is received, the sender immediately sends another DAT packet, goes to state 3 and waits for an ACK response. If no response is received after the end period and retries of the data transfer, the BIU goes to state 5 and is de-used. If the ACK is received as the result of the last data transfer, the transmitter temporarily goes to state 4. From there, if there is more data to send, the BIU returns to state 2 and waits for another RSM message before sending. If there is no more data to send, the BIU will stay in state 4 until another RSM message is received, and then return to state 0 by sending a no data acknowledgment (NAD) message. When state 5 is reached by any of the paths shown in FIG. 17, the BIU must reconnect and resume data transfer before going to state 0 again.

It should be understood from the foregoing that the present invention represents a significant advance over the bus interface device used in the conventional branch network of the present invention. In particular, the present invention provides a novel technique for completing an interactive TALK mode without a host computer while simultaneously completing a logical connection between two user devices on a network. In addition, the present invention provides a REMOTE mode in which a user controls a remote bus interface device to store messages in the remote device. In addition, while specific embodiments of the invention have been described in detail for purposes of illustration, it should be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not limited to the appended claims.

Claims (18)

A bus interface device for use in a branch office computer network having a plurality of user devices connected to transmit and receive information via a communication bus and a bus, the bus interface device being connected to a plurality of user devices to the bus interface device. Means for transmitting or receiving information therefrom, means for connecting the bus interface device to a communication bus via a plurality of logical ports, a common mode in which information does not pass from the user device to the bus, and a user Logical switching means for each user device that can be switched between connected modes in which information from the device is passed to the bus through its corresponding logic port and information received from the bus through the same logical port is passed to the user device. Said logic switching means being provided to a remote device by a user device via a bus. The information from the user device from the connected connection mode is automatically transmitted to the connected remote device when there is a specific symbol in the information, and the information from the connected remote device is transferred to the bus interface device and the information is transferred. A bus interface device, characterized in that it is possible to switch to a discourse mode that is automatically output to a user when there is a specific symbol. 2. The apparatus according to claim 1, wherein said bus interface device is further provided with information processing means coupled to said logic switching means and connected to a common mode to receive information from a user device, said information processing means having a symbol of each information therein. Bus interface device having means for echoing back to the source of the signal and means for identifying a command in the information. 3. The method of claim 2, wherein said command identification means switches said logic switching means to a conversation mode in which said information processing means receives information from both a remote user device connected with a user device. And thus means for echoing the sign of each information to its originating source operate on both sources of information, and the information processing means detects a particular sign in the information from both sources and goes to another source. And means for detecting all information accumulated before a particular symbol in response to the transmission of the. 3. The method according to claim 2, wherein said means for identifying said command switches said logic switching means to a connected mode so as to effect switching said remote bus interface device to a remote mode in which received information is translated for commands to a remote bus interface device. Bus interface device that functions according to the identification of the "remote" command. An apparatus for a branch office computer network having a plurality of user devices connected to transmit and receive information via a communication bus and a bus, the apparatus comprising: at least two of a generating station and a receiving station device arbitrarily designated for connecting the bus and the user device; Information processing means comprising: means for echoing a sign to a source for storing and analyzing a sign of information from a respective user device, a means for identifying a command in the information, and the bus interface device; A first set of terminals connected to each associated user apparatus, a second set of terminals connected to each logical port of the bus, at least one terminal connected to the information processing means, and the terminal by interconnecting Logical switching means having means for forming a message path and said logical switching means being a local user device. For requesting a connection between a means initially acting on a generating station apparatus to switch to a common mode connected to said information processing means, and a user apparatus at a local user apparatus and a receiving station apparatus identified only by name in a CALL instruction; A call request means operated at the originating station apparatus when identifying the CALL instruction in the information processing means, a call request processing means actuated at the receiving station apparatus to determine whether a connection has been made in accordance with the CALL instruction, and the logical switching means. A first link storage means operating in both devices after a successful connection request to switch to the DATA mode in which the local device on one of the first sets of terminals is connected to the port to the bus, and another bus interface connected together. Operated on both devices after a successful connection request to remember the station and port of the device. And a second link storage means. 6. The apparatus according to claim 5, wherein the call requesting means, the call request processing means, the first link storing means, and the second link storing means all function in the same way to complete a logical connection in accordance with a TALK command issued by the generating station apparatus. The apparatus further comprises a discourse switching means operative to configure the logic switching means in the generating station apparatus such that the information processing means receives information from both the local apparatus and the remote apparatus, the information processing means also being from one source. Means for responding to the detection of a particular preference to cause the local and remote devices to be connected to an interactive conversation mode by sending the received information to another source. 6. The method according to claim 5, wherein the call requesting means, the call request processing means, the first link storing means, and the second link storing means all function in the same way to complete a logical connection in accordance with a REMOTE instruction issued by the generating station apparatus. The connection made in the station apparatus is made between the reserved bus port and the information processing means, and the information flowing into the local user apparatus of the producing station is processed for an instruction in the receiving station apparatus, whereby the generating station apparatus is common. A device that appears to be in mode but is actually relaying commands to a receiving station device. 8. The apparatus according to claim 7, wherein said information processing means of the receiving station apparatus is provided with means for processing a message command and storing a message for the receiving station user to process a message indicator. A bus interface device for use in a branch office computer network having a plurality of user devices connected to transmit and receive information via a communication bus and a bus, the bus interface device being connected to a plurality of user devices to the bus interface device. Means for transmitting information to or receiving information therefrom; means for connecting the bus interface device to a communication bus via an equal number of logic ports; and information from the user device passes through the bus for each user device; Logical switching with command mode where no command mode is passed and information from the user device is passed to the bus through its corresponding logic port and information received from the bus through the same logical port is passed to the user device. Means, means for processing a command received from each user device, and the called Means for use when the bus interface device functions as a calling device to transmit the name of the bus interface device to all bus interface devices in the network, and to the called bus interface device having a name that matches the transmitted name. Means for receiving an acknowledgment message from the bus interface apparatus and receiving a connection request acknowledgment message from the called bus interface, and the logical switching means in response to receiving the acknowledgment message. And means for causing the calling device and the called device to be logically connected for the transmission of an additional data message by switching over to. 10. The apparatus according to claim 9, wherein said logic switching means is capable of switching to a discourse mode in which said command processing means is connected to receive information from both a local user device and a connected remote user device. Means for echoing the symbol of each information back to the source from which the symbol is received, so as to transmit the information received from the source to another source so that the information from each connected device appears in the other device; A bus interface device having means for responding to a particular symbol of information. 10. The method of claim 9, wherein the command processing means operates in accordance with a REMOTE command to initiate a connection to a specific port of a remote bus interface device and the particular port is connected to the command processing means at the remote device. Bus interface device on which the device accepts commands from the local device. A method for use in a branch office network having a communication bus and a plurality of user interface devices and a plurality of bus interface devices connected between the buses, the method comprising: detecting a CALL command at a generating station bus interface device (BIU); Identifying the name in the command, requesting access to the recipient station BIU, determining whether the connection was completed at the recipient station BIU, and if the connection can be completed, from the receiving station BIU to the originating station BIU. Transmitting a connection request confirmation message, establishing a first logical data path between the user device and the bus port at the receiving station BIU (remembering the first logical connection), and the user device and receiving station Establishing a second logical data path between the bus ports in the BIU [remembering the second logical connection], and a third logical data path between the ports of the two BIUs. Installing the bus interface method that is characterized by - a third step of storing the received connected to each BIU]. 13. The method of claim 12, wherein the method comprises a first step of detecting a TALK command, wherein the request determining and storing step is also performed in accordance with the detection of the TALK command, the method being further coupled to the user of the information storage and processing module. Modify the first logical connection to connect the device and the bus port, identify a particular symbol in the information received from the producing station user device or the receiving station user device, and according to the particular symbol, receive information received from one source from another source. A method comprising a series of steps to transfer to. 13. The method of claim 12, wherein the method comprises a first step of detecting a BEMOTE command, wherein the requesting, determining, and storing the first and third logical connections is performed in accordance with a REMOTE command, and wherein the second logic And the step of memorizing the connection is executed at the receiving station BIU of the command flowing in from the generating station apparatus by making a connection between the command processing modules in the receiving station BIU of the reserved bus port. 15. The method of claim 14, further comprising the step of executing a MESSAGE command at the originating station BIU apparatus, and executing a MESSAGE at the receiving station BIU including operating a message indicator storing a message that means the command. Way. 16. The method of claim 15, further comprising recovering the memorized message at the receiving station BIU. 15. The method of claim 14, further comprising: introducing a CALL command at the originating station BIU device, and logically connecting the device at the receiving station BIU to the third device. How to include. 13. The method of claim 12, further comprising the steps of: transmitting a data packet from the originating station BIU to the receiving station BIU, receiving a data confirmation message from the receiving station BIU, and in response thereto, transmitting the data packet; Receiving a wait-acknowledge message from the BIU, switching to a receiver driven data transfer mode in response to the wait-acknowledge message, receiving a data resume message from the receiving station, and responding to the data resume message; And retransmitting the last data packet, whereby the data transmission is in sender drive mode until the wait-acknowledge message is received and then in the receiver drive mode.

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