JP3311005B2 - Local area network - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a local area network.

[0002]

BACKGROUND OF THE INVENTION color laser copy (below, CLC
It is needless to say that the scanner and the printer do not need to have a separate type structure, but may be integrated into a stand-alone color copying machine. However, considering the systemization of various printers, scanners, image processing computers, and the like, the advantage of configuring the scanner and the printer as separate units is great. A conventional interface for connecting a CLC scanner and a printer uses an 8-bit parallel transmission for high-speed transmission of large-capacity image signals, and 16 interfaces are used only for parallel transmission. A signal line is required, and if a control signal is included, a cable having a diameter of about 10 mm in which 25 or more signal lines are bundled is required.

[0003]

However, in the above-mentioned conventional transmission, the cable length is limited to within several meters in terms of electric signal attenuation and unnecessary radiation noise, and the expandability of the system is also limited. poor. For example,
It is not easy to output from one scanner to ten printers simultaneously. Therefore, by using an optical fiber instead of an electrical cable, the above-mentioned problems related to the transmission distance and unnecessary radiation noise are solved, and as the link of the optical fiber, the concept of a local area network is introduced to realize the system. Although scalability can be dealt with, there are the following problems in combining these conventional technologies.

That is, the information amount of a color image signal is extremely enormous. For example, when an A4 size is read in full color of 300 dpi, the data amount becomes 47 Mbytes. When this data is stored in a semiconductor memory, the cost of the memory is considerably high. Therefore, in a conventional CLC, a large-capacity memory is not provided by driving a scanner and a printer in synchronization. I have to.

On the other hand, the current LAN protocol has a problem that the real-time communication is impaired because all the data are packetized and transmitted. Therefore, it is necessary to temporarily store data to be transmitted in a memory and transmit the data one by one to a device capable of determining conditions, such as a microprocessor. Therefore, there is a problem that a normal LAN for transmitting data by packetizing the data cannot be used for transmitting the CLC image signal, even if it is a high-speed signal such as FDDI. The present invention enables efficient call control when the information processing device between the calling side and the called side uses a communication line and the calling side and the called side cannot communicate with each other. The purpose is to.

[0006]

The present invention has the following arrangement to solve the above-mentioned problems. That is, in a local area network having a plurality of information processing devices, the first information processing device makes a call to the second information processing.
At this time, a call signal is transmitted from the first information processing apparatus.
A first transmission unit, the first information processing device, and the second
In the third information processing device between the information processing devices of
Receiving the outgoing call signal transmitted by the first transmitting means.
Receiving means for receiving, according to the reception by the receiving means,
The third information processing device is in front of the first information processing device.
The communication line with the second information processing device is used.
Discriminating means for discriminating whether or not, and discrimination by the discriminating means
The first information processing device via the third information processing device.
Communication between the second information processing device and the second information processing device is not possible.
Providing a busy signal indicating that the second information processing is possible
And a second transmitting means for transmitting to the device . Here, the second information processing device is configured to execute the second information processing device.
When receiving the busy signal transmitted by the transmitting means,
The first information processing device is notified of the call signal.
A third sender for sending a disconnection signal for stopping the communication
It has a step.

[0007]

[0008]

[0009]

In the above arrangement, call control is performed when the information processing device between the calling side and the called side uses the communication line so that the calling side and the called side cannot communicate with each other. Since connection can be performed efficiently, channel connection control can be performed smoothly.

[0010]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows a network configuration in which a plurality of scanners and a plurality of printers are connected in a loop by an optical fiber 100 in a local area network according to an embodiment of the present invention. Also, FIG.
Computer 2 between the scanner 202 and the printer 204
FIG. 3 shows a connection mode in which an interface unit (IPU) 203 that provides an interface with the Internet Protocol 01 is interposed. If this IPU function is carded in accordance with the bus of the host computer, it can be mounted on the host computer, and the host computer can be directly connected to the optical fiber network. In this case, up to 123 terminals can be connected.

FIG. 3 shows an example of a conventional connection configuration between a set of a scanner, a printer, an IPU, and a computer. It is desirable that the number of terminals on the network is actually suppressed to about 20 per loop in relation to traffic. For example, it is assumed that the configuration is made up of about 10 scanners and about 10 printers. In this case, if one set of scanner / printer occupies the network,
In the worst case, the other nine scanners / printers may have to wait.

However, it is also possible to simultaneously communicate with ten sets of scanners / printers adjacent to each other. If only one scanner is connected, there is no problem even if a maximum of 122 printers are connected. In general, when communication is performed via a network, a buffer memory for one page is required. However, if an architecture based on real-time communication is adopted, the buffer memory becomes unnecessary by simultaneously starting the scanner side and the printer side. Become.

In the network of this embodiment, 123 Mb
It is specified that the CLC scanner and the printer are connected only by a pair of optical fibers of ps. Further, the image signal and the control signal are time-division multiplexed in one optical fiber,
For full duplex, the optical fiber takes the form of a single ring. This is less reliable in the event of a failure than the FDDI with a double ring, but the network of the present embodiment assumes that a small but large amount of image data is sent, The data transmission efficiency is higher than the exchange FDDI. In addition, the optical fiber is resistant to extraneous noise, and even if an error of several bits occurs in the transmitted image signal, it does not cause a serious problem. Therefore, in the network of this embodiment, for example, the FCS ( An error detection mechanism such as a frame inspection sequence is omitted.

Further, 4B / 5B used in FDDI
Since the coding system has poor line use efficiency, a CMI code bioration synchronization system is used instead. This method has the advantages that the clock can be easily extracted, the line utilization efficiency is high, and the TDM (time division multiplexing) is easy, as compared with the FDDI. Here, 125
Since the Mbps optical fiber is time division (TDM),
It looks as if the signals shown below are wired individually. Image signal <I-Channel> Printer start signal <I-Channel> Page synchronization signal <I-Channel> Line synchronization signal <I-Channel> Control command signal (ASCII) <C-Channel> Of these, the control command The signal is a synchronous RS
-232C, and transmits various control commands of layer 3 or higher in OSI.

Further, these signal groups are <I-Channel
el> element and <C-Channel> element, and <I-Channel> is a circuit-switched bulk
Bearer channel through which data flows, <C-Ch
<annel> is a control channel for controlling the connection of <I-Channel>. Note that here, 100 Mbp
In order to handle ultra-high-speed C-Channel data of s or more, an 8-bit one-chip microcomputer may be used as a processor for controlling the I-Channel, for example.

<Physical Interface> The standard of the optical fiber network according to this embodiment is defined as follows. Loop shape: Single loop Material: Quartz glass Core / cladding diameter: 50/125 microns Fiber type: GI-50 Connector type: FC type Wavelength: 1.3 microns Clock: 144 Mbps Image signal: 17.8 Mbytes / s
ec (max) Control signal: 140 Kbps Modulation signal: CMI Frame synchronization: Bioration of bit 0 1 Frame length: 128 octets Multiframe: 16 frames Access method: Network distributed type Maximum number of nodes: 123 Maximum distance between nodes : 1Km Maximum loop total extension: 123Km Call control format: Connection type Exchange format: Circuit switching Error control: None (Image data) Parity check (Control packet)

<Data Link of Optical Fiber Interface> One frame is divided as shown in FIG. 4 in order to time-division multiplex an image signal and a control signal. Where Tx
D0 to TxD7 and Rx Terminal ID
Are transmitted using Serial Data bits. Since both have an 8-bit configuration, 16 consecutive frames are required to transmit a total of 16-bit data. FIG. 5 shows the frame structure. In FIG. 5, F [n] (n = 0... 15) indicates a relative frame number counted from the frame of M3 = 1. The 16 frames from F [0] to F [15] are called a frame set. Since the CMI encoding and the bioration synchronization method are known technologies, their detailed description is omitted here.

<Address Control (Physical Address)> Terminals such as a scanner, a printer, an IPU, and a host computer have independent physical addresses (Terminal) as described below.
ID Number). Terminal ID 0 Invalid address Terminal ID 1 Master terminal address (real) Terminal ID 2-124 General terminal address (real) Terminal ID 125 Reserved Terminal ID 126 System address (virtual) Terminal ID 127 Broadcast (virtual) book In the system of the embodiment, a terminal having an address of ID = 1 is set as a master terminal, and the other terminals are set as general terminals. This master terminal can also function as a general terminal. Further, the master terminal can be installed as an independent device.

The architecture of the optical loop / local area network according to the present embodiment is of a distributed network type. That is, each terminal has a network function. Also, customarily, a part of a node that receives an optical signal is called an "incoming line" and a part that transmits an optical signal is called an "outgoing line". And each node is an I-Channel of the outgoing line from there.
Only el traffic is managed. Thus, the network of this embodiment is characterized in that it is basically a network distributed type. Needless to say, the master terminal should be processed more often than the general terminal, but network-specific tasks such as call setup, busy control, and call disconnection are distributed to each terminal. .

A method for processing a command byte received by a general terminal is as follows. 1. Same Rx Terminal I as own terminal ID number
The command byte of D is read and not transmitted to the next terminal. 2. Rx Terminal I different from own terminal ID number
The command byte of D is ignored and retransmitted to the next terminal without any processing. 3. When an outgoing line is blocked, when a call setup packet using the outgoing line is received, a predetermined bit is set and transmitted to the next terminal. (The call setup packet is sent out in Broadcast Cast mode.)

The master terminal also performs the following processing. That is, 1. Suppress command bytes for physically non-existent and quiescent terminals. 2. A general terminal in an operating state is periodically searched, and if there is no response from the terminal, it is regarded as a stationary state (DM). 3. Initialization reception from a stationary terminal. 4. Recovery operation at the time of network congestion. <Topology> Terminal ID numbers are connected in ascending order of numbers as shown in FIG. 6, and packets and data flow in the direction of the arrow in the figure.

<Call control> As the call control, for example, a terminal A
The normal communication sequence when (ID = 3) sends an image signal to terminal B (ID = 7) is as follows. 1. Terminal A sends a "call" packet to terminal B. (Broadcast) 2. Each terminal (ID = 4, 5, 6) between terminals AB is <I
-Channel> is checked, and if it is free, the "calling" packet is passed without any processing, and if it is busy, the "calling with the busy flag set" packet ("calling disabled") is passed. 3. Terminal B receives the “calling” packet received
If not, after preparing the printer,
A "call accepted" packet is returned to terminal A, and if a busy flag is set, a "disconnected" packet is returned to terminal A. 4. When receiving the “call reception”, the terminal A sends the image data to the <I-Channel>. 5. Terminal A sends a "disconnect" packet to terminal B. (Broadcast) 6. Each terminal (ID = 4, 5, 6) between terminals AB is <I
After taking the procedure of releasing -Channel>, pass the "cut" packet without processing. Assuming that <I-Channel
If there is a problem in opening e>, the packet is passed through the "disconnection with error flag set" packet. 7. The terminal B confirms that the error flag of the “disconnection” packet is not set, and returns a “disconnection acceptance” packet to the terminal A. (When setting the busy flag, the MSB of the parity byte is inverted.)

FIG. 7 shows the flow of the above sequence. Although the flow shown in the figure focuses on only the terminal A and the terminal B, FIG. 8 shows a detailed sequence in which other terminals are also taken into consideration. Note that the communication end / reception end command marked with * in FIG. 7 is a concept of an upper layer, and is transmitted in an “information packet” described later.

In FIG. 8, since the "call" packet is transferred while being examined by each terminal, it can be seen that a delay occurs each time the packet passes through the terminal. The "incoming call" reception packet is sent to the terminal 7 because the loop is one-way,
The loop returns to terminal A. Further, since there is no software delay for the image data, the image data reaches the terminal B from the terminal A in substantially real time.

FIG. 9 shows that a terminal located between terminals A and B is set to <I
<Channel> is used. In this case, the terminal 4 receives the “call” received from the terminal A.
By setting the busy flag of the packet, the packet is changed to a “calling disabled” packet and transmitted, and the terminal B is notified that this communication cannot be performed.

<Packet> The types of packets are as follows. Outgoing call packet: Terminal transmits to other terminals <I
-Channel>. Incoming call acceptance packet: Indicates that the call can be received. Disconnection packet: Indicates that use of <I-Channel> is to be terminated. Disconnection acceptance packet: Indicates that <I-Channel> has been released. Information packet: Indicates that the packet includes information of an upper layer. Reject packet: A packet when the network cannot accept a terminal request.

<Packet Structure> FIGS. 10 to 12 show main packet structures. <State Transition Diagram> The general terminal takes one of the following states. Stopped: Power is off DM: State not recognized by master terminal (Disconnect Mode) Idle: State recognized by master terminal by issuing INIT Response: Waiting for permission to use I-Channel State Ready: A state in which the I-Channel can be used. Transmitting / Receiving: A state in which an image signal is being communicated in the I-Channel. FIG.

<Timer> A general terminal has a timer described below and manages state transition. T. 1: After the calling terminal issues a calling packet, the timer is started. If neither the incoming call reception nor the disconnection request is returned even after the timer times out, a call packet can be issued again. The number of retransmissions of this packet is Up to one time, at which point it is determined that the network is busy. T. 2: General terminal is T. INIT once every 2 seconds
Can issue packets. This is repeated until DISC or UA is received, and when a UA packet is received, the state shifts to an idle state. When the DISC packet is received, it stays in the DM state and After waiting more than 3 seconds
T. 2 is reset, and retransmission of the INIT packet is started again. Here, T. 1 = 60 seconds 2 = 5 seconds 3 = 60 seconds N.I. 1 = 3 times.

<Transmission of Image Data> Image data is transmitted using an I-channel (D0 to D1015 in a frame). The first pixel of each scanning line is written in D0, and when the average transmission speed of image data is lower than the average transmission speed of the I-channel (17.8 Mbytes / sec), data to be sent may be lost. In this case, a NULL frame is transmitted. For this speed matching, a FIFO of about 128 bytes is required.

<Description of Circuit Configuration> Next, modulation and demodulation of an optical signal according to this embodiment will be described. FIG. 14 is a block diagram illustrating modulation and demodulation of an optical signal in the local area network according to the embodiment. In FIG. 1, an input optical signal is converted into an electric signal by a demodulator 1 including a photoelectric conversion element (avalanche diode), and CMI demodulation is performed. Synchronization signals for multiplexing the signals are produced by bit 1 bioration. For demodulation, the self-running clock of the PLL 2 is used, and the phase synchronization is performed by returning the demodulation result to the PLL 2 again. The clock generated by the PLL 2 further includes a counter 3 for controlling the entire sequence,
Others are also supplied. Since the CMI modulation / demodulation is known, a detailed description thereof will be omitted. Further, the modulation method here is not limited to the CMI method, and may be, for example, a 4B5B method.

The input signal demodulated by the demodulator 1 includes an image signal, a control signal, and the above-mentioned bioration bit. Therefore, for example, in order to extract only the image signal, the counter circuit 3 generates a signal whose logic is "true" at a portion corresponding to the image signal portion, and drives the shift register 11 with the clock of only that portion. To The shift register 11 also performs serial / parallel conversion of the image signal at the same time, converts the image signal into an 8-bit parallel signal, and sends it to a printer (not shown). In addition, 8
The conversion into the bit parallel signal is performed in consideration of compatibility with the conventional printer engine, and the image signal may be transmitted as it is serially.

The control signal portion of M 2 shown in FIG. 5 from the output of the demodulator 1 is sent to the shift register 4. M2 is a bit assigned to transmit a serial / control signal, and transmits a receiving terminal ID number and serial transmission data as shown in FIG. Since the serial control signal transmitted in one frame is one bit, 16 frames are required to transmit the data shown in FIG. This is called 16 multi-frame transmission. As for the command, one byte is transmitted in 16 multi-frames. Then, the command is sent in a series of 5 to 10 bytes.
This is called a packet. For example, since the outgoing call packet has a 6-byte structure, 96 frames are required to receive this packet.

The head of the packet is a serial / synchronous signal (M
3). When transmitting the first byte of this packet, the M3 bit in the frame is also set to "1" and transmitted. This allows the receiving side to know the start of packet reception. Then, when a packet starts to be sent, the packet must be sent without interruption. However, when there is no packet to be transmitted, the invalid byte (NULL byte) is continuously transmitted. Therefore, the receiving side needs a circuit that ignores the NULL byte. Therefore, according to the present method, it is possible to transmit a packet between packets.

The control code subjected to serial / parallel conversion by the shift register 4 is input to the microprocessor 7. The input method is fetched by DMA transfer or read operation from the microprocessor by interruption. Further, since the serial data is sent with the receiving terminal number, the microprocessor 7 can immediately retransmit the packet to the output side shift register when the packet is not addressed to the terminal itself. However, when a packet relating to the own terminal is being transmitted, the transmission of the packet is waited for, and then the packet addressed to the other terminal is transferred. The transmission of the packet is performed via the shift register 6, and in sequence,
The operation opposite to the operation of shift register 4 is performed.

The delay circuit 5 is a circuit for delaying the image signal of <I-Channel>, and is not provided for general terminals. That is, it is provided only for one master terminal existing in one LAN. In addition, the use is mentioned later. The multiplexer 9 combines the control signal (C-Channel) from the shift register 6 and the image signal (I-Channel) from the delay circuit 5 to form a frame in the format shown in FIG. The switching of the multiplexer 9 is performed by a switching signal generated by the counter circuit 3. In the case of a transceiver for a general terminal not having the delay circuit 5, an image signal (I-Channel) irrelevant to the terminal itself is retransmitted without processing immediately after reception. Therefore, the data delay has only a minimum required fixed delay in the modem. This state is referred to as "through" the data.

On the other hand, the control signal (C-Channel)
The data of this channel is not "through" because of the non-constant delay introduced by the microprocessor 7 and the processing of the packet. In addition, since the processing speed of the microprocessor is slow, the data is transmitted just after being delayed by a multiple of one frame in order to transmit the data in accordance with the format shown in FIG.

The transceiver of the local area network according to the present embodiment is used for transmitting one frame, for example.
Since it takes 1 microsecond, when a maximum of 123 terminals are connected, it takes at least 873 microseconds for a command to go through a loop. Since this value does not take into account the processing speed of the microprocessor of each node, a considerable delay actually occurs.

Although the difference between the I-Channel data and the C-Channel data is not a serious problem in the specification of the network, the difference between the I-Channel data and the C-Channel data is small.
If the call control of the annel is delayed, I-Channel
Since the throughput of 1 will be affected, the smaller the delay, the better. Therefore, a method for making the delay by the microprocessor substantially zero will be described later. The multiplexer 8 switches between <I-Channel> and <I-Channel>.
When −Channel> is used for another node, the multiplexer 8 passes a signal from the delay circuit 5. On the other hand, when the own terminal is transmitting, the signal from the shift register 12 is passed.

In the case of the LAN according to the present embodiment, <I-Ch
The switching of “annel>” may be performed gradually, so that invalid data may flow. However, actually for future expansion, <I-Channel
l> is also synchronized with the frame. Then, the frame synthesized by the multiplexer 9 is converted into an optical signal subjected to CMI conversion by a modulator 10 including a laser diode, and transmitted to the next node. A frame synchronization signal extracted from the demodulator 1 by a few clock delays is used as a frame synchronization signal used for CMI bioration in the modulator 10. The delay of several clocks is to synchronize with the data delay caused by the latch for absorbing the waveform rounding generated in the multiplexers 8, 9 and the like.

<Explanation of Main Network> As described above, the delay circuit 5 of FIG. 14 is provided only in the master terminal. This is gradually delayed in general terminals <I-Chan
This is for adjusting the one-cycle cumulative delay of nel> such that the total delay amount is one frame (or a multiple thereof) at the master terminal. In general, when an optical fiber is connected on a loop to form a LAN, it is impossible to connect the optical fibers in a normal circuit switching mode. However, in the present embodiment, circuit switching can be realized because of the presence of the delay circuit 5. Hereinafter, regarding the main part of the delay circuit,
This will be described with reference to the block diagram shown in FIG.

FIG. 15 is a detailed block diagram of the delay circuit 5 of FIG. In the figure, the I-Channel data input to the shift register 20 is converted there into an 8-bit parallel signal. This is because the access time of the random access memory (hereinafter referred to as RAM) 22 is as slow as 35 nanoseconds, and the apparent data rate is reduced by performing the processing in parallel. Since the parallel output from the shift register 20 flows at the I-Channel clock rate, the D-type latch (hereinafter referred to as D latch) 2 is used.
1 holds data for 8 clocks.

The data rate in this embodiment is 55.5 nanoseconds, and a C-MOS type RAM can be used. Since this RAM is used to delay data for a predetermined time, the address An only needs to be incremented regularly. That is, the RAM 22 sets the delay amount of the I-Channel data to 1 byte (8 bytes) as described later.
Control in bit units. The output On of the RAM 22
Are latched by a D latch 23 for waveform shaping.

I-Chn shaped by D latch 23
The nel data is delayed by barrel shifter 24.
This barrel shifter 24 can control the delay amount from the outside, unlike a normal shift register. The control signal is a barrel select signal. In the present embodiment, the barrel shifter 24 has at most 0
Since it is only necessary to obtain a delay amount of 7 bits, a delay amount of 8 bits or more is realized in combination with the RAM 22.

The output of the barrel shifter 24 is received by the D-shaped latch 39 for waveform shaping, and is input to the FIFO 41. Since the signal that has made a round of the optical fiber loop contains jitter, the delay amount is rarely a positive multiple of 1 bit, and the value changes with temperature changes or the optical fiber is physically transmitted. It changes even if you just bend it. Therefore, a RAM capable of obtaining a delay amount of an arbitrary positive number of bits is provided.
The combination of the barrel shifter 22 and the barrel shifter 24 alone is not sufficient. The FIFO 41 absorbs a delay variation of 1 bit or less.

Here, the address control circuit of the RAM 22 will be described. The RAM 22 performs writing and reading while the I-Channel elapses a time equivalent to eight clocks.
These write time and read time are each equivalent to 4 clocks. Therefore, data selector 2
Reference numeral 5 alternately switches address information of two systems every four clocks.

The write address is generated by the counter 26, and the read address is formed by the adder 28 and the D latch 27. The outputs of the D latch 27 are all added to the adder 28.
When a binary "1" is input to the other input An and a clock is applied to the D latch 27, this system operates as a binary counter. When the value applied to the input An is “2”, D
The output of the latch 27 is incremented by "2", and An
, The output of the D latch stops at the value at that time.

D latches 29, 30, 32 and NAND
The gate 31 changes the “Increment” which is a control signal from the microprocessor 7 from logic “L” to “H”.
Becomes "H" for one clock. As a result, the value "2" is supplied to An, and the output of the D latch 27 advances by 1 with respect to the counter 26. Similarly, D latches 35, 36, 38 and NAND gate 37 provide:
When the “Decrement” signal changes from logic “L” to “H”, “0” is applied to An, and D latch 2 is applied.
The output of 7 lags the counter 26 by one.

<Delay amount measuring circuit> In the above delay circuit,
Since the amount of delay to be set varies depending on the number of terminals in the optical loop, it must actually be measured. Hereinafter, a circuit for measuring the amount of loop delay of the optical loop will be described with reference to FIG. In the same figure, the same components as those in FIG. 15 are denoted by the same reference numerals, and their description is omitted.

The measurement of the delay amount shown in FIG. 16 is performed at the master terminal. At the master terminal, modulator 1
The built-in clock 50 is used as the zero clock.
The switch 51 is a data selector for switching the clock to the modulator 10 for the master terminal / general terminal. In such a configuration, when the optical output of the modulator 10 returns to the demodulator 1 through a loop, the frame synchronization signals SYNC1 and SYNC are output from both the modulator 10 and the demodulator 1.
C2 is obtained respectively. Both SYNC signals are applied to the SR latch 52, and the output Q is output from SYNC1 to SYNC.
The logic "H" is maintained for up to two. The counter 53 is RS
The flip-flop 52 counts the number of clocks at which the logic becomes "H" to measure the amount of loop delay.

The counter 53 is reset by the frame synchronization signal SYNC1 of the modulator 10 and starts counting at the same time. Since the output of the counter 53 is read by the microprocessor 7, the output of the
NC2 latches into parallel shift register 54. The obtained delay amount is a relative delay amount between the transmission frame and the reception frame, and its value does not exceed the transmission time of one frame. The value set in the delay circuit 5 is obtained as follows. That is, [set value] = [number of clocks required for transmission of one frame] − [actual round trip delay amount]
(1)

As described above, according to this embodiment,
An optical fiber composes a local area network, one optical fiber is divided into a packet channel and a circuit channel by time division, and a signal having a slow command system is transmitted through the packet channel. By transmitting a high-speed signal in a data system efficiently through a circuit channel, an interface between a full-color scanner and a printer can be realized without having an expensive page memory, and 10 to 20 scanners can be realized. There is an effect that the printer can be interconnected at this interface like a LAN.

In the block diagram showing the modulation and demodulation of the optical signal shown in FIG. 14, the shift register 11 is used as the LAN interface for the printer, and the shift register 11 is not used as the interface for the printer and the scanner. The shift register 12 may be provided independently for each of the LAN interfaces. At this time, the attribute is clarified by the terminal identifier in the packet so that the command for the scanner and the command for the printer are not mixed up.

In the block diagram shown in FIG. 16, the inputs SYNC1 and SSYNC of the RS flip-flop 52 are shown.
Cross YNC2 and parallel shift register 5
By exchanging SYNC2 input to the enable terminal of No. 4 with SYNC1 input to the clear terminal of the counter 53, the calculation by the above equation (1) becomes unnecessary.
The value set in the delay circuit 5 can be made to coincide with the actually measured value. That is, [set value] = [actual value]
... (2). The present invention may be applied to a system including a plurality of devices or to an apparatus including a single device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus.

[0054]

According to the present invention, a call can be made when an information processing device between a calling side and a called side uses a communication line and the calling side and the called side cannot communicate with each other. Since call control can be performed efficiently, channel connection control can be performed smoothly.

[Brief description of the drawings]

FIG. 1 is a diagram showing a network configuration in which a plurality of scanners and a plurality of printers are connected in a loop by an optical fiber in a local area network according to an embodiment of the present invention;

FIG. 2 is a diagram showing a connection mode in which an interface unit for providing an interface with a computer is interposed between a scanner and a printer;

FIG. 3 is a diagram showing an example of a conventional connection configuration between a set of a scanner, a printer, an IPU, and a computer;

FIG. 4 is a diagram showing a frame structure of time division multiplexing;

FIG. 5 is a diagram showing a multi-frame structure of M2 bits.

FIG. 6 is a diagram showing a terminal ID number and a data flow;

FIG. 7 is a diagram showing a call control communication sequence when transmitting an image signal;

FIG. 8 is a diagram showing details of another call control communication sequence;

FIG. 9 is a diagram showing a terminal between terminals A and B being an I-Channel.
Diagram showing a sequence in use,

FIG. 10

FIG. 11

FIG. 12 is a view showing a structure of a main packet;

FIG. 13 is a state transition diagram of a general terminal,

FIG. 14 is a modulation / demodulation block diagram of an optical signal in a local area network according to the embodiment.

FIG. 15 is a block diagram showing a main part of the delay circuit;

FIG. 16 is a diagram showing a circuit for measuring the amount of loop delay of an optical loop.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Demodulator 2 PLL 7 Microprocessor 8, 9 Multiplexer 10 Modulator 24 Barrel shifter 26 Counter 27 D latch 28 Adder 52 RS flip-flop 54 Parallel shift register

Continuation of front page (56) References JP-A-59-66259 (JP, A) JP-A-3-147543 (JP, A) JP-A-63-1227 (JP, A) JP-A-59-119933 (JP JP-A-59-230349 (JP, A) JP-A-56-23057 (JP, A) JP-A-62-23256 (JP, A) JP-A-57-11555 (JP, A) 60-9243 (JP, A) JP-A-62-189841 (JP, A) JP-A-63-174449 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 12/427

Claims (2)

(57) [Claims] In a local area network having a plurality of information processing devices, when the first information processing device makes a call to the second information processing, a call signal is transmitted from the first information processing device. A first transmitting unit, and a third information processing device between the first information processing device and the second information processing device, receiving a call signal transmitted by the first transmitting device. Receiving means, and whether or not the third information processing apparatus uses a communication line between the first information processing apparatus and the second information processing apparatus in response to reception by the receiving means Determining means for determining whether or not communication between the first information processing apparatus and the second information processing apparatus via the third information processing apparatus is impossible according to the determination by the determining means A busy signal indicating the second information. Local area network and having a second transmission means for transmitting to the processing unit. 2. The second information processing device, upon receiving a busy signal transmitted by the second transmission means, causes the first information processing device to stop communication for the call signal. local area network according to claim 1, wherein a third transmission means for transmitting a disconnect signal.