JP3042822B2 - Bus contention control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system in which a plurality of communication devices are connected to a communication control device via a common bus, and more specifically, the communication device communicates via the communication control device. The present invention relates to a bus contention control method for controlling contention of bus access when performing a bus contention.

[0002]

2. Description of the Related Art Conventionally, as this kind of technology, for example, there is a D-channel contention control system described in "ISDN I Series International Standards and Technologies" published by the Telecommunications Association, pages 89-95. In this method, the communication control device in the network terminating device includes two sets of communication channels configured by a serial bus.
A plurality of communication devices are connected as terminals by 2B and a set of D channels for transferring signals and packet data. When a plurality of terminals transmit the competitive signal on the D channel, the D channel is looped back in the communication control device and connected to those terminals. The plurality of terminals compare the transmitted signal and the returned signal one bit at a time by a D-channel contention control circuit, and a terminal that matches both obtains a communication priority, and a terminal that does not match determines the other terminal. And determines that the collision has occurred, and suspends the start of communication. The priority is given to give priority to signal (signaling) information over communication data. In addition, although the priorities are classified by class, for terminals that have failed transmission once, the priority is temporarily increased by one, so that transmission is completed equally in the same class. To be there. Furthermore, when a plurality of terminals of the same class and the same priority access at the same time, one terminal can always complete transmission by detecting data collision.

[0003]

However, the contention control system described above is of the serial bus type, and the following problem arises when this is applied to a parallel bus communication system. First, comparison cannot be made on a bit-by-bit basis. Also, if multiple terminals access in the same class and with the same priority, bus contention will be controlled by detecting data collision, but in the case of a parallel bus, collision will occur independently for all bits. Therefore, depending on the contents of the transmission data, all terminals that have accessed simultaneously may fail to transmit. If this is strictly controlled, each bit of the parallel bus is simultaneously compared by the competition control circuit for each bus line, and the results are integrated to determine a match, which complicates the circuit configuration of the terminal. There is a disadvantage that.

The present invention solves the above-mentioned drawbacks of the prior art and provides a bus contention control system in which the bus contention control in a communication system in which a plurality of terminals are connected to a communication control device via a parallel bus is simplified. The purpose is to do.

[0005]

In order to solve the above-mentioned problems, a bus contention control system according to the present invention includes a plurality of communication devices for transmitting data in synchronization with a timing signal, and a data transmission by a plurality of communication devices. In a communication system including a communication control means for controlling the communication and a transmission path for connecting a plurality of communication devices to the communication control means in common and transferring data in a bit parallel manner, each of the plurality of communication devices has a unique identification display. Wherein the plurality of communication devices generate a transmission request signal for transmitting data on the transmission path including the identification display, and the communication system further connects the plurality of communication devices to the communication control means in common and transmits. A first signal line for transferring a request signal to the communication control means in a bit-serial manner; A plurality of communication devices each compares a transmission request signal transmitted by itself and a transmission request response signal received from the second signal line, and when both do not match, The communication device includes a conflict control unit that determines a collision, and transmits a transmission request signal to the first signal line in synchronization with the timing signal before transmitting data to the transmission path. When the transmission request signal transmitted by itself matches the transmission request response signal received from the second signal line, the data is transmitted to the transmission path, and when the transmission request signal does not match, the data transmission is stopped.

According to the present invention, there is also provided a communication system as described above.

[0007]

According to the present invention, the first and second signal lines for serial contention control are provided corresponding to bit-parallel transmission paths. The communication device transmits a transmission request signal in synchronization with the timing signal prior to frame transmission of the parallel data. The transmission request signal is looped back by the communication control means and returned to each communication device as a transmission request response signal. The contention control means of each communication device compares the two signals and detects their coincidence and disagreement,
Contention of data transmission from a plurality of communication devices is controlled.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a bus contention control system according to the present invention; FIG. 1 shows an embodiment of a bus contention control system according to the present invention, and FIG. 2 shows a signal format in the embodiment. In this embodiment, a communication control device 10 is provided in a network termination device (not shown) of a communication system. The communication control device 10 is a circuit that controls access of the communication terminals 11 to 14 to a communication network. The communication control device 10 and the terminals 11 to 14 are a data bus 15 which is a transmission / reception transmission path for transmitting byte data in a bit parallel manner, a transmission / reception timing signal line 16 for transmitting the transmission / reception timing signal,
And the contention control bus 19. Connections in these transmission directions are all wired and connections.

The communication terminals 11 to 14 independently divide the indefinite-length data 101 into fixed-length data, that is, frames, of a predetermined length in synchronization with the transmission / reception timing signal 100.
In this embodiment, the communication terminal device transfers the data to the communication control device 10 on the data bus 15 at a transmission speed of 32 Mb / s. Of course, the terminal devices 11 to 14 of the present embodiment have a function of receiving data from the data bus 15. However, the data reception function,
It is not an essential function of the present invention and is not necessary for understanding the present invention.

[0010] The contention control bus 19 is a bit serial round trip 2
Lines, which are sent by the sender 17 in the communication controller 10.
And the receiver 18, and is configured to return the upward signal transmitted by the terminals 11 to 14 in the downward direction. The communication control device 10 generates the transmission / reception timing signal (SRQC) 100 of FIG. 2 on the transmission / reception timing signal line 16 for the purpose of controlling the transfer of the terminals 11 to 14 via the data bus 15. As shown in FIG. 2, the transmission / reception timing signal 100 has a frame transmission / reception period T of 23.6 μs in this embodiment, during which one frame is transmitted / received. The frame transmission / reception period T includes a low-level contention control period t in the present embodiment, and this period t is a period for the terminals 11 to 14 to acquire a transmission right prior to transmission of a frame. The length t of the period is 6.3 μs in this embodiment.

The communication terminals 11 to 14 may basically have the same configuration, and each terminal is provided with a unique identification, for example, terminal numbers 0H to 3H. The identification display does not necessarily need to be a number, but may be an identification code. In this embodiment, the number of terminals 11 to 14 is four.
It is needless to say that the present invention is not limited to this number but can be effectively applied to an arbitrary number of terminals. Terminals 11-14
Includes a contention control circuit 21 having a D-channel contention control function in a conventional terminal. When a transmission request occurs, the contention control circuit 21 transmits the transmission request data (SRQD) 102 (FIG. 3) to the contention control bus 19 in synchronization with the start (fall) of the contention control period t of the transmission / reception timing signal 100 described later. To send to.

The transmission request data (SRQD) 102 is transmitted to the terminals 11 to 14
Is a signal indicating a request to transmit data on the data bus 15, and has three regions as illustrated in FIG. That is, the data format is a 5-bit data format including a 1-bit class area 102a, a 2-bit priority area 102b, and a terminal number area 102c. The transmission request data 102 is transferred on the contention control bus 19 in a bit serial manner. Class area 10
2a indicates the type of the data 101 transferred on the data bus 15, and if the data 101 is signal (signaling) information, 2a
The binary value is “0”, and if it is communication information, the binary value is “1”. The priority of the contention is such that signal information has priority over communication information. The priority area 102b indicates the priority within the same class, and its initial value is a binary value "11". When transmissions from terminals of the same class conflict, the terminal that has failed to acquire the transmission right has a binary value of “1” in the priority area 102b each time.
Counted down by one. If successful, the default value is "11"
Is reset to The terminal number area 102c is an area in which the number of the terminal to be transmitted is stored. In this embodiment, the smaller the number, the higher the priority in the same class and the same priority.

The transmitting terminal transmits and receives the transmission / reception timing signal 10
The transmission request data 102 is sent to the contention control bus 19 in the contention control period t of 0, which is returned from the communication control device 10 and received as the transmission request response data 103 by the terminals 11 to 14. The transmitting terminal compares the transmission request response data 103 with the transmission request data 102 bit by bit by the contention control circuit 21. The collision is detected by giving priority to the binary value "0" and determining whether the values match or not. The terminal in which both match, that is, in which no collision is detected, determines that it has acquired the transmission right, and synchronizes with the data 101 in synchronization with the end (rising) of the period t.
Is transmitted to the data bus 15. The terminal that has detected the mismatch, that is, the collision, immediately stops sending the transmission request data 102 at that time. Then, by manipulating the value of the transmission request data 102 according to the conditions at the time of collision detection,
The next contention control period t is captured, and the transmission right is started again. The operation of this value will be described later with a specific example of collision.

In the case of data reception, the terminal number 102c included in the transmission request response data 103 sent from the communication control device 10 to the contention control bus 19 is received. It is ready to receive a transmission frame 104 of data 101 on 15.

FIG. 4 shows that four terminals 11 to 14 are connected to a bus 15 at the same time.
Shows the contention operation until transmission is completed for all terminals when the terminal is accessed. As shown in FIG. 5, the transmission request data 10
The value “0” of the class area 102a of No. 2 indicates that the data to be transmitted is the signal information, and the value “11” of the priority area 102b indicates the value of
This is the second access. Since the value of the priority area 102b of the data 102 of the terminal 12 is “10”, which is one countdown from the initial value “11”, it is understood that this is the second access of the data information. The data 102 of the terminals 13 and 14 indicates that this is the first access of the data information, and the only difference is the terminal number area 102c. With simultaneous access of 4 terminals 11-14, all terminals 11-
Three conflicts occur before 14 completes the transmission.

The first is a competition between all the terminals 11 to 14. In this case, in the class area 102a, only the terminal 11 has the value “0” and the others have the value “1”, so that the terminals 12 to 14 other than the terminal 11 detect a collision. Terminals 12-14 that detected the collision
Stops the transmission of the data 102 and shifts to re-access with the value of the data 102 as it is. Since the terminal 11 does not detect any collision thereafter, the terminal 11 transmits the transmission frame 104 after the transmission of the data 102 is completed. In this example, the terminal 11 having a higher priority of the class 102a than the others terminates the transmission.

In the second access, the terminal 11 does not access in this example, so that the three terminals 12 to 14 compete. In this case, since all the class areas 102a have the value “1”, no collision due to the class area 102a is detected, and the next priority area
This is due to the collision detection at 102b. In the priority area 102b, only the terminal 12 has the priority value "11" of the terminals 13 and 14.
The value is “10” which is one smaller than the value. Therefore, when the second bit of the priority area 102b appears in the transmission request response data 103, the terminals 13 and 14 detect a collision. Since the terminal 12 having the higher priority in the same class does not detect the collision, only this completes the transmission. The other terminals 13 and 14 are in the priority area
102b is decremented by one to make a binary value "10" and re-accessed.

Assuming that the terminals 11 and 12 do not access any more, in the third contention between the terminal 13 and the terminal 14, the class area 102a and the priority area 102b are the same, but the terminal number area 102c has 13 is the value "10" and the terminal 14
Is the value "11", so that the terminal 14 detects a collision in the second bit of the terminal number area 102c. Therefore, the terminal 13 having the smaller terminal number starts transmission, and the terminal 14 having the larger terminal number counts down the value of the priority area 102b by one, and then re-accesses.

Since the last remaining terminal 14 is not accessed by the terminals 11 to 14, no conflict occurs. Therefore terminal 14
Shifts to transmission without detecting the collision of the transmission request data 102.

In this embodiment, there are four terminals 11 to 14 and two classes of transfer information on the data bus 15. The present invention is not limited to these numbers, but includes the class area 102a and the priority area 102b in the transmission request data 102.
By changing the number of bits of the terminal number area 102c, it is possible to adapt to an arbitrary class and priority type and the number of terminals.

[0021]

As described above, according to the present invention, in the contention control of the transfer on the bit parallel data bus, by providing the bit serial contention control bus, it is possible to compare the contention control data bit by bit. The contention control circuit of the terminal can be simplified. Also, by including the terminal identification display in the transmission request data, one terminal can always complete transmission even in the same class and the same priority.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an embodiment of a bus contention control system according to the present invention.

FIG. 2 is a time chart illustrating an example of a signal waveform in the system of FIG. 1;

FIG. 3 is a configuration diagram showing an example of transmission request data in the embodiment shown in FIG. 1;

FIG. 4 is a time chart showing an example of a competitive operation in the system of FIG. 1;

5 is a diagram illustrating an example of transmission request data in the example of the contention operation illustrated in FIG. 4;

[Explanation of symbols]

 10 Communication control device 11-14 Communication terminal 15 Data bus 16 Transmission / reception timing signal line 17 Sender 18 Receiver 19 Competition control bus 21 Competition control circuit

Claims (3)

(57) [Claims] 1. A plurality of communication devices for transmitting data in synchronization with a timing signal, communication control means for controlling data transmission by the plurality of communication devices, and a plurality of communication devices shared by the communication control means In a bus contention control system for a communication system including a connection path for transferring the data in a bit parallel manner, the plurality of communication devices each have a unique identification display, and the plurality of communication devices are Generating a transmission request signal for transmitting the data on the transmission path including an identification display, the communication system further connects the plurality of communication devices to the communication control means in common, and transmits the transmission request signal A first signal line that transfers the communication request to the communication control means in a bit-serial manner; and the transmission request signal is returned from the communication control means to be transmitted in common to the plurality of communication devices as a transmission request response signal. A plurality of communication devices, each of which compares the transmission request signal transmitted by itself and the transmission request response signal received from the second signal line, When the two do not coincide with each other, the communication device includes a conflict control unit for determining a collision, and the communication device transmits the transmission request signal to a first signal line in synchronization with the timing signal before transmitting data to the transmission line. In the comparison by the contention control means, if the transmission request signal transmitted by itself matches the transmission request response signal received from the second signal line, the data is transmitted to the transmission path, and there is no match. And a bus contention control method in which data transmission is stopped. 2. The bus contention control method according to claim 1, wherein the transmission request signal is a first signal indicating whether data transferred on the transmission path is communication information or signal information. Data, second data indicating the priority of the communication device, and third data including an identification of the communication device, wherein the contention control means converts the signal information in the first data from the communication information. A bus contention control method characterized by a higher priority. 3. A plurality of communication devices for transmitting data in synchronization with a timing signal, communication control means for controlling data transmission by the plurality of communication devices, and the plurality of communication devices being shared by the communication control means. And a transmission path for connecting and transferring the data in a bit-parallel manner, wherein the plurality of communication devices each have a unique identification, and the plurality of communication devices include the identification. Generating a transmission request signal for transmitting the data on a transmission line, the communication system further connects the plurality of communication devices in common to the communication control unit, and transmits the transmission request signal to the communication control unit. The communication system further includes: a first signal line that transfers data in a bit serial manner; the communication control unit includes a return unit that returns the transmission request signal to a transmission request response signal; A second signal line for transmitting the transmission request response signal to the plurality of communication devices in a bit serial manner in common, wherein each of the plurality of communication devices transmits the transmission request signal and the second signal line transmitted by itself. Comparing the received transmission request response signal with the received transmission request response signal, and when the two do not coincide with each other, the communication device includes a conflict control unit that determines that there is a collision, and the communication device synchronizes with the timing signal before transmitting data to the transmission path. Transmitting the transmission request signal to the first signal line, and when the transmission request signal transmitted by the transmission control signal coincides with the transmission request response signal received from the second signal line in the comparison by the contention control means, A communication system, wherein data is transmitted to the transmission path, and if the data does not match, the data transmission is stopped.