JPS5990443A - Method and device for processing bus competition among plural terminals of bus connection - Google Patents

Abstract

PURPOSE:To decrease the call connecting time without giving a limit to the number of contained terminals by constituting a calling receviving mode with a specific procedure, selecting one calling terminal with a repeated calling terminal selecting mode by another procedure and allocating data to the terminal. CONSTITUTION:The calling receiving mode is performed by the following procedures. That is, a network terminator NT inserts a control bit pattern generated by a circuit 60 to a control time slot P of an outgoing frame via a circuit 30 and transmits it, and informs the reception of a calling request to each terminal. Then, the presence of the calling terminal is detected at a circuit 40 by a flag of a calling request display time slot R of an incoming frame. When existing, the result of detection is informed to each terminal by a control bit pattern via a circuit 80, a pattern generating circuit 50, a selecting circuit 70 and a pattern inserting circuit 30. Then, the calling terminal selecting mode is executed. In this case, when plural terminals are recognized for the existence, to which terminal the calling request is allocated is decided by collating the coincidence with a preset value at each bit of a binary address assigned to each terminal to decide a specific address.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bus contention processing method and device between a plurality of bus-connected terminals.

Currently, an open integrated service digital network (l5lr) N: Int.
egrated 5 services Digital
Active research is being carried out in various places toward the construction of a network. In particular, in the 15DN in-home wiring system, since a plurality of terminals are connected to one network termination device, there is a desire for an in-home system that is easy to access from the terminals, has small hardware scale, and is inexpensive. The bus connection method, which connects a network termination device and multiple terminals on the same upstream (each terminal → network termination device) and downlink (network termination device → each terminal) bus, requires (4) simple and low-cost in-house wiring. While it has the advantage of being expected to reduce costs,
The problem is how to handle bus contention between multiple terminals. Conventional bus contention processing methods include polling and TD.
MA (Time Division Multiple
Access), C8MA/CD (Carrier 8
ense MultipleAccess/Col I
is ion Detection), etc. are known. Polling is a method of avoiding bus contention by allowing the network terminal equipment to sequentially determine whether a call request is issued or not to each terminal, but it has the disadvantage that the connection time increases as the number of terminals increases. Furthermore, with TDMA, two methods have been considered: one is to allocate control bits provided within a frame to each terminal, and the other is a method in which control bits are allocated to each terminal in multi-frames. However, in the former method, the transmission rate of the bus There is a trade-off relationship with the number of terminals, and the number of accommodated terminals is actually limited, and the latter method has the disadvantage that the connection time increases as the number of accommodated terminals increases.

Furthermore, although there is virtually no limit to the number of terminals that can be accommodated in the C8MA/CD system, there is a drawback (5) in that the connection time becomes extremely long as the number of calling terminals increases.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a bus contention processing method and device that can shorten call connection time without actually limiting the number of accommodated terminals.

Still another object of the present invention is to provide a bus contention processing method and device that has small hardware scale, is inexpensive, and has simple access processing.

In order to achieve these objectives, the bus contention processing method and device between a plurality of bus-connected terminals of the present invention provides a method and a device for handling bus contention between a plurality of terminals connected to a bus. In a system in which communication between the terminals and/or communication between the terminals and other networks is realized via the network terminal device, the network The downlink frame generated by the terminal device is composed of downlink data and control bits each consisting of at least one bit, and is sent to the downlink bus, and is also composed of upstream data and a call request bit, each consisting of at least one bit. The uplink frame to be transmitted is synchronized with the downlink frame (6) and sent to the uplink bus, hereinafter 0).
A series of operating procedures of ~■ [(i) By setting the control signal in the network terminal device f to a certain pattern (pattern for accepting call requests), the call requests to each terminal are not accepted. Notify me of something.

(2) Each of the terminals detects the control bit pattern, and if it determines that the call request is accepted, it uses the call request bit to reply to the network terminal device as to whether or not there is a call. However, since each of the terminals shares the call request bit, a conflict occurs when two or more terminals request a call. ■
The network terminating device observes the call request bit and detects a small (
After determining whether or not there is a call request from one or more terminals, the control bit is set to one of two types (call request pattern and no call request pattern) for accepting the call request. By setting one type of pattern, each terminal is notified of the determination result as to whether or not there is a call request. ” configures the call reception mode, and if the calling terminal is not fully warmed up in the above operation If there is at least one terminal, 23 of each terminal allocated in advance
1 (For each bit of the address η, the following operators 1...
l [-■ The calling terminal among the terminals has a specified bit value in its own address that is a predetermined value (1'
0"), and uses the call request bit to reply to the network terminating device with the determination result of match or mismatch. ■The network terminating device observes the call request bit. After determining the response result of the match and mismatch, the step 2 above is performed.
Seed pattern or another 2a! By setting the pattern to one of the patterns, each terminal is notified of the response determination result of match≠non-match. ” by repeating the calling terminal selection mode the same number of times as the number of bits of the binary address, a specific calling terminal is selected from one or more calling terminals, and one of the uplink data is selected. The present invention is characterized in that a portion or all of the calling terminal is allocated to the selected calling terminal.

The present invention will be explained in detail below with reference to the drawings (8) do.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the same figure, the reference alphabet NT is the network terminal equipment, and the reference alphabet S
T, , ST, , ..., STN is the terminal, reference number 1
Reference numeral 2 indicates a downlink bus, reference numeral 2 indicates an uplink bus, and reference numeral 3 indicates a transmission path. NT and N (N is an integer of 2 or more) terminals ST, , ST, , ..., STN are on the same downlink (network termination device → each terminal) and uplink (each terminal → network termination device) bus, respectively. It is connected to the. Further, a binary address is assigned to each of the N terminals 8T, 8T, . Here, it is assumed that the transmission line 3 is connected to the communication network by two wires, four wires, or multiple pairs of wires. Further, the communication network may be a congregational network or a local network, and the form of the network does not matter. Network termination device NT and N terminals 8 in FIG.
Before describing the details of ThST2, . . . , STN, the frame formats of the downlink bus 1 and uplink bus 2 will be described first.

(9) FIGS. 2(a) and (1) show examples of the frame formats of the downlink bus 1 and downlink bus 2 in FIG. 1, respectively.

In the same figure, the reference alphabet F is the time slot for frame bits, the reference alphabet is the data time slot, the reference alphabet P is the control time slot, the reference alphabet R is the call display time slot, and the reference alphabet G is the guard time slot. show. Here, it is assumed that the uplink frame is synchronized with the downlink frame generated by the network terminal device. Bus contention processing is necessary when there are multiple terminals accessing the data time slot D in the frame of the uplink bus shown in FIG. 2(b). Therefore, the network terminal equipment NT and terminals 8T, , 8T, ..., S shown in FIG.
The operating principle of the bus contention processing method and device of the present invention will be described by explaining a detailed block diagram of the TN.

3(a) and 3(b) show detailed block diagrams of the network terminal equipment NT and terminals ST1, ST2, . . . , STN in FIG. 1, respectively.

(10) In the figure, reference number 3 is a transmission line, reference number 10 is a transmission line interface, reference number 20 is a frame generation circuit, reference number 30 is a control bit pattern insertion circuit, reference number 40 is a flag detection circuit, reference number Reference numeral 50 indicates a call request non-acceptance and match/mismatch pattern generation circuit, reference numeral 60 indicates a call request acceptance pattern generation circuit, reference numeral 70 indicates a selection circuit, reference numeral 80 indicates a control circuit with a counter, reference numeral 90
Reference numeral 100 is a signal sent to the downlink bus, reference numeral 100 is a reception signal from the uplink bus, reference numeral 110 is a frame synchronization circuit, reference numeral 120 is a control bit pattern detection circuit, reference numeral 130 is a control circuit with a counter, and reference numeral 140 is a control circuit with a counter. Flag generation Z insertion circuit, reference number 150 is the terminal body, reference number 160 is the call request signal, reference number 170 is the call permission signal, reference number 180 is the reception signal from the down bus, reference number 190 is the reception signal to the up bus. Each of the sending signals is shown.

FIG. 3(a) shows an example of a detailed block of the network termination device NT in FIG. and is supplied to the frame generation circuit 20.

In the frame generation circuit 20, as shown in FIG. 2(a),
A frame is generated by adding frame pick l-F.

The output of the frame generation circuit 20 is supplied to a control bit pattern insertion circuit 30, which inserts a control bit pattern into the control time slot P shown in FIG. On the other hand, the received signal 100 from the uplink bus is supplied to the network via the transmission line ink face 10 and the transmission line 3, and at the same time, the flag detection circuit 4
0 is also supplied, and the flag detection circuit 40 detects the flag of the call display time slot R shown in FIG. 2(b). The output of the flag detection circuit 40 is supplied to a control circuit 80 with a counter, which generates a selection signal for controlling the selection circuit 70 and a control signal for controlling the call request cloth≠none and match-unmatch pattern generation circuit 50. Call request reception pattern 60 and call request non-reception and match ≠ mismatch pattern generation circuit 5
One of the 0 patterns is selected by the selection circuit 70 and supplied to the control bit pattern insertion circuit 30.

(12) FIG. 3(b) shows the terminal ST+ (j=1.2.
....

An example of the detailed block of N) is shown.

In the figure, a received signal 180 from the downlink bus is supplied to a control circuit with a counter 130 via a frame synchronization circuit 110, and an output from a control bit pattern detection circuit 120 for detecting control bit patterns. On the other hand, the counter control circuit 130 receives a call request signal 160 from the terminal main body 150 and sends a call permission signal 170 to the terminal main body 150. Furthermore, the output of the terminal main body 150 and the output of the control circuit with counter 130 are supplied to a flag generation/insertion circuit 140 and sent to the upstream bus as a transmission signal 190 to the upstream bus. Here, we calculate the total processing time including flag detection and control bit pattern insertion at the network termination equipment, control bit pattern detection and flag insertion at each terminal, and the round-trip propagation delay time for the maximum distance between one terminal of the network termination equipment. The case where one frame period is set to be longer than the added value will be explained (13). However, in the opposite case, the use of the control time slot and flag display time slot will be changed to l (l is 2 or more). integer)
It may be limited to once per frame.

Next, the operations shown in FIGS. 3(a) and 3(b) will be explained in detail using the flowcharts shown in FIGS. 4 and 5, respectively.

In both figures, P indicates the control bit pattern generated by the network termination device NT in Figure 1, and P in Figure 2 (
It is inserted into the control time slot P of the downlink frame shown in a). The P2'''00'' pattern means acceptance of a call request, and is generated by the call request acceptance pattern generation circuit shown in FIG. 3(a).

P="11" means that the flag is detected by the flag detection circuit 40 in FIG. .) means. On the other hand, P-'''t
o'' means that the flag was not detected by the flag detection circuit 40 in FIG. (14).P-“11” and P-2”10” are shown in Fig.
In a), the call request cloth≠none and match are generated by the mismatch pattern generation circuit. Note that different patterns may be given to call request cloth≠none and match≠unmatched, but the same pattern is assumed here to simplify the explanation. R is the terminal 811+ in FIG. 1, (1:l
:IP2'...,N) indicates the call originating flag R, which is inserted into the control time slot of the upstream frame shown in FIG. 2(b). "R-0" means that the flag is not set k n 1 +
+ means that a flag is set. R-0'' is configured so that the terminal does not send any signal in the control time slot R of the uplink frame. Conversely, when multiple terminals set flags in the same frame, flag collision occurs; The flag transmission waveform is selected so that cancellation does not occur.For example, one method is to set the flag code format common to all terminals to be ``1-'', which has a balanced flow. M means the number of bits of the binary address assigned to each terminal (15). m is a positive integer less than or equal to M. L (m) is
To simplify the explanation, we will use the lower m of the binary address here.
Assume that it indicates the value of the bit.

Therefore, L (M) is the value of the most significant bit.

FIG. 4 shows an operation flowchart of the network terminal device NT of FIG. 1 or its detailed block shown in FIG. 3(a), and will be described in detail with reference to related drawings.

First, in the network terminal device NT, the control circuit 80 with a counter and the selection circuit 70 shown in FIG. After being inserted into the control time slot P of the downlink frame via the pattern insertion circuit 30, it is sent to the downlink bus to notify each terminal that a call request is being accepted.

Next, the network terminal device NT checks whether or not a flag is set in the call request display time slot 14 of the uplink frame corresponding to the downlink frame using the flag detection circuit 4 in FIG. 3(a).
Detected at 0. If there is no calling terminal, R1-"0" is detected, and if there is at least one calling terminal, R-1" is detected, so the flag detection result is 3) control circuit with counter 8
0, call request cloth no closing and match mismatch pattern generation circuit 50, selection circuit 70 and control bit pattern insertion circuit 3
0, P=″′10″ (corresponding to it=1″) or P
="11" (corresponding to R="'1"), each terminal is notified of the absence of the call requesting terminal.

The above series of operations is defined as call reception mode.

Next, if there is no call requesting terminal, the operation procedure of the call reception mode is repeated again. FIG. 4 shows a flowchart of the call reception mode.

On the other hand, if there is at least one calling terminal, the counter of the counter control circuit 80 in FIG. 3(a) is set to M (corresponding to m = M in FIG. 4), and so on. Execute a series of operating procedures (defined as calling terminal selection mode) described in .

Next, the calling terminal selection mode will be explained, but before that, the prerequisites for selecting a calling terminal will be described. When each terminal and the network terminal device recognize that one or more call requesting terminals exist at the same time (17), each terminal is assigned which call requesting terminal is allowed to make a call request. The principle of the present invention is to determine a specific address by checking whether each bit of the base address matches a predetermined value ("0" or "1"). Therefore, in the calling terminal selection mode, it is a condition that the order of collation of each bit of the binary address of each terminal and the predetermined value are the same for the network terminating device and each terminal. It needs to be decided in advance. Although the order in which the bits of the binary address are compared may be arbitrary, in order to simplify the explanation, it is assumed here that the bits are compared starting from the most significant bits. In addition, it is assumed that the predetermined value is '0'.If the network terminating device itself does not need to know the address of the selected calling terminal, the network terminating device It is not necessary to know the predetermined values.When the network termination equipment enters the calling terminal selection mode, the first
The flag of the call request time slot of the uplink frame (2) is detected by the flag detection circuit 4° (18) in FIG. 3(a). Based on the above assumption, the value of the second most significant bit (Mth bit) of the address of the terminal among the call requesting terminals is predetermined in the call indication time slot of the first upstream frame. Only terminals that match the value (currently 0") are allowed to set the flag. Therefore, when the network terminal equipment detects R-"1", the Mth bit of the address is set to 0". It is confirmed that there is at least one calling terminal that matches . On the other hand, when R2°“OIT is detected, the Mth bit of the address is
Since it can be seen that there are no calling terminals that match 0'', it can be confirmed that the Mth bit of the address of all calling terminals is 1''.

The detection result of the flag detection circuit 40 in FIG. When it is 0”, P2”1
0", and when R = "1", P = "II" is inserted into the control time slot, and each terminal is notified of the matching result of the (19) Mth bit of the address. The value of the counter in the counter control circuit 80 of FIG.
The flag of the call request time slot of the th uplink frame is detected, and the presence or absence of the matching A mismatching terminal of the address of the (M-1) th bit is determined.
M-1) Notify each terminal of the match A mismatch matching result of the bit. Furthermore, the control circuit 8 with counter shown in FIG. 3(a)
Let the value of the counter in 0 be M-2. Repeat in the same way up to the first bit (the least significant bit) of the terminal's binary address. Through such an operation, one terminal among one or more calling terminals can be selected. A flowchart at this time is shown in the calling terminal tracing mode in FIG. In Figure 4, L(m) −〇 or L(m) = 1
This operation can be omitted if the network terminating device does not need to know the address of the selected calling terminal.

In the data transmission mode shown in FIG. A calling terminal means a terminal using all or part of the data time slot D in FIG. 2(b).

)≠ne and notifies each terminal of P=="ll", and the second
Each terminal is made to recognize that all or part of the data time slots 1-D shown in FIG. 3(b) are in use. When the network terminal device detects I%=“o”, it shifts to the call reception mode again.

A flowchart at this time is shown in the data sending mode of FIG.

FIG. 5 shows each of the plurality of terminals ST, , ST, , in FIG.
..., STN or its detailed block shown in Fig. 3 (
This figure shows an operation flowchart of b), and will be described in detail with reference to related drawings. First, when the terminal power is turned on, the flag generation/insertion circuit shown in Fig. 3(b) causes the call display time slot shown in Fig. 2(b) to be set in a state where the flag is not set, that is, R-'0''. Next, the terminal detects the bit (21) pattern of the control time slot P of the downlink bus shown in FIG. 2(a) using the control bit pattern detection circuit 120 shown in FIG. 3(b). .p) OO”, the counter control circuit 130 and flag generation in FIG. 3(b)≠insertion circuit 1
40, send it to the upstream bus as R="Q" and send it to the upstream bus P2"
This operation is repeated until "o o" is detected. When the terminal detects P="'00" and the call request signal 160 in FIG. 3(b) is in the call request state, the fifth The terminal repeats the call acceptance mode shown in FIG. 5 unless the two conditions mentioned above are simultaneously satisfied although the preparatory operation for transitioning to the calling terminal selection mode shown in the figure is executed.

Next, the calling terminal selection mode shown in FIG. 5 will be explained.

When the control bit pattern detection circuit 120 of FIG. 3(b) detects P=“00” and the call request signal 160 is in the call request state, the flag generation/insertion circuit 140 A flag is set in the call display time slot shown in FIG. 3(b), that is, it is sent to the upstream bus as R=''1''. Since the network terminal equipment NT notifies the presence or absence of the calling terminal after the next frame, the terminal should definitely receive P="ll".

(22) However, it is unclear whether the calling terminal is other than the calling terminal. Therefore, when a pattern other than P=“11” is detected, it means that a failure has occurred in a part of the system. Therefore, chapter 1 corresponds to the mark in FIG. 5, and is assumed to be connected to the failure routine. So the terminal is P
After confirming that = "ll", the counter of the counter control circuit 130 shown in FIG. 3(b) is set to M. The terminal then matches each bit l of the binary address assigned to it with a predetermined value (°'0'' in the present description).

This verification is performed using a predetermined number l18i (in the current explanation, in order from the upper bit to the tenth bit of the address).

Therefore, the terminal first checks whether the value of the most significant bit 1- (@Mth bit) of the address matches 10'' as shown in Figure 3 (b).
Judgment is made by a control circuit with a counter, and if there is a match, 1 is also -"1"
, when there is a mismatch, it is sent to the upstream bus as R-"Q". Next, the network terminal equipment notifies the terminal of the result of match≠non-match using the control time slot of the downlink bus. The terminal is
If P2 ``11'' or (23) is detected in the downstream frame after sending R = ``'1'' to the upstream bus, or if R = ``'0'' is detected in the downstream frame after sending it to the upstream bus. If "P-10" is detected, it is determined that the own terminal is being selected, and the address bits to be verified are shifted (in FIG. 3(b), the value of the counter of the control circuit with counter 130 is (corresponds to decreasing R by 1) Repeat the above operation.Meanwhile, when the terminal
After sending `` to the upstream bus, P = '''1 in the downward frame of the fire.
When a control pattern other than 1" is detected, it means that a failure has occurred in a part of the system. In Fig. 5,
It is assumed that the error routine corresponds to the mark and is connected to the failure routine. Furthermore, if a control pattern other than P:"10" is detected in the next downlink frame after a terminal sends R = "'0" to the uplink bus, it is determined that the own terminal has not been selected and sends the Shift to call acceptance mode. From the moment it is determined that the terminal itself has been selected, the terminal shifts to the data transmission mode shown in FIG.

At this time, the counter control circuit 130 of FIG. 3(b) notifies the terminal body 150 that the call is permitted by the call permission signal 170, and also sets R2'''1'' to (24
) Send to the upbound bus. Furthermore, during data transmission, R="1"
'' to the upstream bus and informs the network terminal equipment that data is being sent. When the terminal finishes sending data R
= II Q II is sent to the upstream bus to notify the network terminal device that data transmission has ended, thereby transitioning to call acceptance mode.

Note that it is also possible to omit the operation of P-'10'' in the call request reception mode of the flowchart shown in FIG. The call connection time can be shortened since the time period is 100%.

The effects of the present invention will be explained by giving specific examples. Assuming that the period of one frame is 0.125 m5, it is 128 (=2
Assume that five terminals are connected to a network termination device.

At this time, the call connection time for one person is TA = (2+7)Xo, 1
It is expressed as 25m1, and when calculated, it is 1.125m.

becomes. On the other hand, the call connection time TA' when using the TDMA method in which multi-frames are assembled and control bits are assigned to each terminal is TA' = 128 x O, 125
It is expressed as m-, and when calculated, it becomes 15 + n fields,
According to (25) of the present invention, call connection time can be significantly shortened even when there are a large number of terminals.

In addition, the explanation so far has assumed a communication system in which each terminal accesses the communication network via a network termination device, but in the present invention, by looping back at the network termination device, communication between terminals is possible. It is clear that it can also be applied to communication systems.

Furthermore, in the system based on the principles of the present invention, there is no need to assemble multiple frames, and there is no need to detect collisions between flag display time slots, so the hardware scale can be reduced.

As described in detail above, according to the present invention, it is possible to provide a bus contention processing method and device that can shorten call connection time without substantially limiting the number of accommodated terminals. Further, according to the present invention, it is possible to provide a bus contention processing method and device that has small hardware scale, is inexpensive, and has simple access processing.

(26)

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention,
In the same figure, reference letters NT are network terminal equipment, fij letters S'L”t, ST!, .=, STN are terminals, reference number 1 is down bus, reference number 2 is up bus, reference number 3
indicate the respective transmission paths. Figures 2 (a) and (b) are diagrams showing examples of frame formats for the downlink bus and the uplink bus, respectively. In the figures, the reference alphabet F indicates the time slot for frame bits, and the reference alphabet letter R indicates the time slot for data. The reference letter P indicates a control time slot, and the reference letter G indicates a guard time slot. FIGS. 3(a) and 3(b) are block diagrams showing details of the network termination device NT and the terminal, respectively.
Reference numeral 3 is a transmission line, reference numeral 10 is a transmission line interface, reference numeral 20 is a frame generation circuit, reference numeral 30
Reference number 40 is a control bit pattern insertion circuit, reference number 40 is a flag detection circuit, reference number 50 is a call request signal absent and match 4 mismatch pattern generation circuit, reference number 60 is a call request reception pattern generation circuit, reference number (27). 70 is a selection circuit, reference numeral 80 is a control circuit with a counter, reference numeral 90 is a sending signal to the down bus, reference numeral 10
0 is a received signal from the upstream bus, reference numeral 110 is a frame synchronization circuit, reference numeral 120 is a control bit pattern detection circuit, reference numeral 130 is a control circuit with a counter, reference numeral ] 40 is a flag generation insertion circuit, reference numeral 150 is the terminal body, reference number 160 is the call request signal, reference number 170
Reference numeral 180 indicates a call permission signal, reference numeral 180 indicates a signal received from the downlink bus, and reference numeral 190 indicates a signal sent to the uplink bus. 4 and 5 are diagrams showing flowcharts of the operations of the network terminal device and terminal, respectively, where reference letter P is a control bit pattern, reference letter R is a flag, and reference letter M is a control bit pattern assigned to each terminal. Number of bits of base address, L(m)
is the lower m of the binary address (28) Figure 1 (0) (b) Figure 2 (0) Figure 3

Claims (2)

[Claims] (1) A network termination device and a plurality of terminals are connected to each other for uplink (each terminal → the network termination device) and downlink (the network termination device →
In a system in which the terminals are connected to the same bus, and communication between the terminals or communication between the terminals and other networks is realized via the network termination device, the downlink frame includes The control time slot is configured such that an uplink frame synchronized with the downlink frame includes a flag display time slot, and the network terminal device generates the downlink frame and detects the flag in the flag display time slot at the same time. , the call request acceptance and the flag detection result are notified to each terminal using the control time slot, and each terminal observes the control time slot (1) and receives a notification from the network terminal device. detecting the content, and when receiving a call request acceptance notification, responds the call request to the network terminal device by setting a flag in the flag display time slot only when there is a call request, and also notifies the flag detection result. , only when there is a call request, it is determined whether each bit of the address assigned to each terminal matches a predetermined value (0" or 1") in a predetermined order. By a series of operations of determining each frame and sending a response to the network terminal equipment by setting a flag in the flag display time slot when a match is found, one or more 1. A method for handling bus contention among a plurality of terminals connected to a bus, characterized in that a specific calling terminal from among the calling terminals is given permission to use the uplink bus. (2) The network termination device and each of the plurality of terminals are connected to each other for uplink (each terminal → the network termination device) and downlink (the network termination device →
(2) Communication between the terminals or communication between the terminals and other (2) networks is realized through the network termination device. , configuring a frame so that the downstream frame includes a control time slot, and the upstream frame synchronized with the downstream frame includes a flag display time slot,
a frame generation circuit for generating the downlink frame; a flag detection circuit for detecting the flag in the flag display time slot; and a circuit for accepting a call request and detecting the flag by inserting a bit pattern into the control time slot. at least a notification content display pattern generation circuit for notifying each terminal of the output result of the above, and a frame counter for calculating the number of frames that is the same as the number of bits of the binary address assigned to each of the terminals. The network terminal device is configured to include a frame synchronization circuit, a notification content display pattern detection circuit for detecting the bit pattern of the early control time slot and detecting the notification content, and a notification content display pattern detection circuit for detecting the notification content. The output receiving unit includes at least a flag generation (3) circuit for generating a flag to be inserted into the flag display time slot according to the notification content, and another frame counter having the same function as the frame counter. A bus contention processing device between a plurality of bus-connected terminals, characterized in that each of the terminals is configured as follows.