JPH0439938B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a so-called multi-drop system in which a plurality of terminals are connected to one transmission path, and in particular, transmission control for controlling transmission from each terminal. Regarding the method.

[Conventional technology]

Conventionally, this type of transmission control method uses a polling method or a collision detection method.

The polling method, as shown in Figure 5,
Apart from the terminals 10 ₁ to 10 _o , a master controller 90 for controlling the serial data bus 20
The master controller 90 inquires (polles) whether there is a transmission request to each terminal by transmitting an appropriate transmission control code and a terminal number assigned to each terminal to the serial data bus 20. ). On the other hand, if there is no transmission request, the polled terminal returns an end code, and if there is a transmission request, it transmits data in an appropriate transmission format.

On the other hand, in the collision detection method, as shown in the flowchart of FIG. Set the
After a predetermined time delay (step 2'), the process returns to step 1'. If the bus is not in use, one byte of data is transmitted from the output port, and the transmitted one byte of data is received from the input port (step 3'). A comparator compares the 1 byte of data sent and received above,
It is checked whether they match (step 4'), and if they do not match, the process returns to step 1' after a predetermined time delay in step 2'. On the other hand, if they match, it is checked whether the transmission has been completed (step 5'), and if it has not been completed, the process moves to step 3'.

[Problem that the invention seeks to solve]

However, the polling method requires a master controller separate from the terminal, which has the disadvantage of making the system expensive. Another disadvantage is that when there are many terminals on the bus, polling takes a lot of time, which shortens the time that data is sent to the bus, making it impossible to use the bus effectively. It was hot.

On the other hand, the collision detection method has the disadvantage that processing such as comparing data in the bus controller of each terminal and setting a timer value to a timer becomes complicated.

[Purpose of the invention]

An object of the present invention is to provide a transmission control method that can be implemented with an inexpensive system that does not require a master controller.

Another object of the present invention is to provide a transmission control method that can effectively use a bus.

Still another object of the present invention is to provide a transmission control method that is relatively easy to process.

[Means for solving problems]

The transmission control method according to the present invention allows multiple terminals to
In a so-called multi-drop connected to a main transmission path, a different terminal number is assigned to each terminal, and each terminal has at least a synchronization field containing synchronization information and a first field containing its own terminal number.
a synchronization signal sending means for sending out a synchronization signal having an address field and an address field to the transmission path; a synchronization signal detection means for detecting the synchronization signal on the transmission path; and a call field including at least call information and data. a paging signal transmitting means for transmitting a paging signal having a second address field including a destination terminal number to the transmission path; a paging signal detection means for detecting the paging signal on the transmission path; and a synchronization signal detection device. A first timer value is set, which is calculated according to a predetermined arithmetic expression from the terminal number included in the first address field of the synchronization signal detected by the means and the own terminal number. and a first timer that acquires the first transmission right when the first timer times up if the calling signal detecting means does not detect a calling signal before the first timer times up. a transmission right acquisition means, a signal monitoring means for monitoring whether or not there is a signal on the transmission path, and a destination terminal number included in the second address field in the paging signal detected by the paging signal detection means. is activated when the terminal number does not match the own terminal number, and a second timer value predetermined corresponding to the own terminal number is set each time the signal monitoring means determines that there is a signal on the transmission path. a second timer;
If the synchronization signal is not detected by the synchronization signal detecting means before the second timer times up, acquiring the second transmission right when the second timer times up. and when the second or first transmission right acquisition means acquires the second or first transmission right, if there is no data to be transmitted, the synchronization signal transmission means is activated to transmit the synchronization signal. If there is data to be sent to the transmission path, the calling signal sending means is first activated to send the calling signal, then the data to be sent is sent to the transmission path, and the sending of the data is completed. transmission control means that subsequently activates the synchronization signal sending means to sequentially send out synchronization signals; It is characterized by having means for receiving subsequently sent data when the number matches.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 4 is a system configuration diagram showing an example of a multi-drop configuration to which the transmission control method according to the present invention is applied. In this embodiment, five terminals 10 ₀ ,
10 ₁ , 10 ₂ , 10 ₃ , and 10 ₄ are connected to serial data bus 20 . Each terminal _10i
(0≦i≦4) is a bus transceiver 30 for transmitting and receiving signals on the serial data bus 20;
A setting switch 40 such as a dip switch for setting a terminal number, an input/output device 50 for inputting and outputting data, and a timer 6 for setting a timer value.
0. Memory 7 with program and work area
0, and bus transceiver 30, input/output device 5
0, a timer 60 and a memory 70.

Note that the input/output device 50 included in each terminal 10 _i may include a keyboard, a display, a printer, and the like. Further, the terminal numbers set by the setting switch 40 for each terminal _10i are "0", " ₁ ", and "2" corresponding to the terminals 10 ₀ , 10 1 , 10 ₂ , 10 ₃ and 10 ₄ , respectively. ”, “3”, and “4” are assigned.

FIG. 1 is a block diagram showing the configuration of each terminal _10i shown in FIG. 4. As mentioned above, the control device 80 is composed of a microprocessor, which is shown divided into blocks according to functions.

The bus transceiver 30 includes a parallel/serial converter (hereinafter abbreviated as P/S converter) 31 for converting parallel data from the control device 80 into serial data and transmitting the serial data onto the serial data bus 20. It has a serial/parallel converter (hereinafter abbreviated as S/P converter) 32 for converting serial data on the serial data bus 20 into parallel data and sending it to the control device 80. The P/S converter 31 also has a function of converting a logical code into a transmission code, and the S/P converter 32
also has the function of converting transmission codes into logical codes. In addition, in this embodiment, the parallel data is
Assume that it is 8 bits.

The memory 70 has a transmission data storage area 71 for temporarily storing transmission data and a reception data storage area 72 for temporarily storing reception data. Of course, although not shown, the memory 70 also has an area for storing programs.

In the control device 80, 81 is the setting switch 4.
This is a terminal number holding unit for holding the own terminal number set by 0. 82 is a synchronization signal sending unit for sending out a synchronization signal, which will be described later. 83
is a calling signal sending unit for sending out a calling signal, which will be described later. 84 is a synchronization signal detection unit for detecting a synchronization signal, and 85 is a call signal detection unit for detecting a call signal. 86 is a timer setting unit for setting a timer value to the timer 60, which will be described later. Reference numeral 87 denotes a transmission/reception control section for controlling transmission and reception of the heart, as will be described later.
88 is a signal monitoring unit for monitoring whether or not there is a signal on the serial data bus 20.

Next, the operation will be described with reference to the flowchart shown in FIG. 2 and the time chart shown in FIG. 3.

FIG. 3a shows an example where there is no data to be sent by each terminal _10i . First, when the power switch (not shown) of the system shown in FIG. _T0 is set in the timer 60 (step 101). Here, assuming that the basic unit of the timer 60 is τ, T ₀ is expressed by the following equation.

T ₀ = (N+1)×τ ... (1) Therefore, the timer values T ₀ of the terminals 10 ₀ , 10 ₁ , 10 ₂ , 10 ₃ and 10 ₄ are τ, 2τ, 3τ, respectively.
4τ and 5τ.

Therefore, the timer 60 of the terminal ₁₀₀ times up first, but when the timer 60 times up at time _t0 (YES in step 102), the timer 60 outputs a time-up signal to the transmission/reception control section 87. When receiving the time-up signal, the transmission/reception control section 87 activates the synchronization signal transmission section 82 to transmit the synchronization signal S to the serial data bus 20 via the P/S conversion section 31 (step 103). Here, the synchronization signal S is
It consists of a synchronization field containing synchronization information SYN, an address field containing its own terminal number (source address) SA, and a check field containing a check code BCC. Therefore, the terminal ₁₀₀ sends "0" as its own terminal number SA. This own terminal number is sent in advance from the terminal number holding section 81 to the synchronization signal sending section 82 by the transmission/reception control section 87, and is temporarily stored therein.

This sent synchronization signal S is transmitted to each terminal, S/P
It is detected by the synchronization signal detection section 84 via the conversion section 32 (YES in steps 103 and 104). The synchronization signal detection unit 84 first detects the synchronization information SYN in the synchronization signal S, and then extracts the synchronization signal detection signal and then the source address SA included in the address field in the synchronization signal S. Then, the source address SA is sent to the timer setting section 86. The timer setting unit 86 stores the received source address SA and the terminal number holding unit 8.
Based on the own terminal number N held at 1, a timer value _T1 is set in the timer 60 at time _t1 (step 105).

Here, _T1 is expressed by the following equation, where W is the total number of terminals connected to the serial data bus 20.

T ₁ ={mod _w (N-SA+W-1)+1}×τ (2) Here, mod _w (X) represents the remainder when X is divided by W. Therefore, in other words, equation (2) can also be expressed as follows.

T ₁ = (N-SA)×τ (when N>SA) = (N-SA+W)×τ (when N≦SA)
...(2') In this case, SA="0" and W="5", so
The timer values T ₁ of the terminals 10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ and 10 ₀ are τ, 2τ, 3τ, 4τ and 5τ, respectively.

Therefore, the timer 60 of the terminal ₁₀₁ initially
A time-up occurs at time t ₂ when time τ has elapsed from time t ₁ (YES in step 106), and a time-up signal is output to the transmission/reception control section 87. Transmission/reception control section 87
When it receives this time-up signal, it acquires the transmission right and determines whether there is any data to be transmitted (step 107). In this case, it is assumed that there is no data to be detected at all terminals, so the process returns to step 103, and the synchronization signal sending unit 82 is activated to send out the synchronization signal S.

In each terminal, the synchronization signal detection section 84 detects the synchronization signal S.
is detected (step 103 and step 108)
YES), the timer setting section 86 as described above.
sets the timer value _T1 in the timer 60 at time _t3 (step 105). At this time, the terminals 10 ₂ , 10
The timer values T ₁ of ₃ , 10 ₄ , 10 ₀ and 10 ₁ are τ, 2τ, 3τ, 4τ and 5τ, respectively. Therefore, the next terminal with timer 60 that times up first is terminal ₁₀₂ .

By repeating the above operations, the synchronization signal S is sequentially transmitted on the serial data bus 20 in the order of the terminals with the smallest terminal number, then the terminal with the highest terminal number, then the terminal with the smallest terminal number, and so on. Sent periodically.

FIG. 3b shows an example where there is data to be sent to the terminal. First, after the power is turned on, a timer value _T0 is set in the timer 60 of each terminal (step 101), and the terminal ₁₀₀ whose timer 60 times up for the first time at time _t0 (YES at step 102) sends out a synchronization signal. The synchronizing signal S is sent from the unit 82 onto the serial data bus 20 (step 103), the synchronizing signal detecting unit 84 of each terminal detects the synchronizing signal S (steps 103 and 104), and the timer setting unit 86 sets the timer value. _T1 is set at time _t1 (step 105).

At time _t2, when time τ has elapsed since time _t1 , the terminal ₁₀
Then, the timer 60 times up and acquires the transmission right, but there is no data to be sent (step
107), the synchronizing signal S is sent out (step 103). This synchronization signal S is detected by the synchronization signal detection unit 84 in each terminal (YES in step 103 and step 108), and the timer setting unit 86
A timer value _T1 is set in the timer 60 at time _t3 (step 105).

At time _t4 , when time τ has elapsed since time _t3 , the terminal 10 ₂
Then, the timer 60 times up (YES in step 106), and the transmission/reception control unit 87 acquires the transmission right. There is data to be sent (step 107)
YES), the transmission/reception control section 87 first activates the calling signal sending section 83 and sends the calling signal E.
is sent to the serial data bus 20 via the P/S converter 31 (step 109). Here, the call signal E includes a call field including inquiry information ENQ, an address field including the destination terminal number (destination address) DA to which data should be sent, the own terminal number (source address) SA that is the sender, and a check field. It consists of a check field containing the code BCC. In this example, terminal 10 ₂ is
Set "3" as the destination terminal number DA and the own terminal number.
Send “2” as SA. These terminal numbers are
Before the calling signal sending unit 83 is activated, the transmission/receiving control unit 87 sends the terminal number holding unit 81 and the input/output device 50 to the calling signal sending unit 83 and temporarily stores it.

This sent out calling signal E is transmitted to each terminal.
Calling signal detection section 8 via S/P conversion section 32
5 (step 109, step 110)
YES). Next, in the terminal 10 ₂ , the transmission/reception control section 87
However, by setting the read/write control signal R/ to read (high level) and sequentially transmitting addresses from the address line AD, the transmit data stored in the transmit data storage area 71 is eliminated. (ON in steps 111 and 112). On the other hand, terminal 1
In terminals other than 0 ₂ , the calling signal detection unit 85
First, by detecting the inquiry information ENQ in the calling signal E, first extract the calling signal detection signal, then extract the destination address DA included in the address field in the calling signal E, and extract the extracted destination address DA. , is sent to the transmission/reception control section 87. The transmission/reception control section 87 stores the received destination address DA and the terminal number holding section 81.
The terminal number N is compared with the own terminal number N held in the terminal (step 113). In this example, since the destination address DA is "3", the terminal ₁₀₃ whose own terminal number N is "3" has the transmission/reception control unit 87 write the read/write control signal R/ (low level) and , by sequentially sending out addresses from the address line AD, the received data that is sent subsequent to the call signal E is stored in the received data storage area 72 (step 114).

On the other hand, terminal 10 whose own terminal number N is not “3”
₀ , 10 ₁ and 10 ₄ , the transmission/reception control section 87 outputs a mismatch signal to the timer setting section 86 . Upon receiving this discrepancy signal, the timer setting unit 86 sets a predetermined timer value T ₂ in the timer 60 at time t ₅ corresponding to the own terminal number N held in the terminal number holding unit 81 ( Step 115). this time
Since _t5 is before the timer 60 times up, no terminal other than the terminal ₁₀₂ that has already acquired the transmission right and is transmitting data will acquire the transmission right, and there will be no conflict for the transmission right. can be prevented,
Data from only one terminal is transferred to serial data bus 2
Sent on 0. In this example, the terminal 10 ₂ is in a transmitting state, the terminal 10 ₃ is in a receiving state, and the other terminals 10 ₀ , 10 ₁ , and 10 ₄ are in a synchronization signal waiting state.

Here, the timer value T ₂ is expressed by the following equation.

T ₂ = (W+N)×τ (3) In the terminal waiting for a synchronization signal, the signal monitoring unit 88 is activated by the above-mentioned mismatch signal and monitors whether or not there is a signal on the serial data bus 20. (Step 116) If there is a signal, a signal present signal is output to the timer setting section 86. Timer setting section 8
In step 6, a timer value _T2 is set in the timer 60 every time this signal is received.
115). Therefore, once the timer value _T2 is set, if the signal monitoring section 88 detects a signal on the serial data bus 20 before the timer 60 times up, the loop of steps 115→117→118→116→115 is completed. Alternatively, the operation continues in a loop of steps 117→118→116→117.

Now, on terminal ₁₀₂ that is sending data,
Data transmission ends at time _t6 (step 112
(YES), the transmission/reception control section 87 activates the synchronization signal sending section 82 to send out the synchronization signal S to the serial data bus 20 (step 103). This sent synchronization signal S is detected by the synchronization signal detection section 84 in each terminal (step 103,
118 YES and step 119 YES). As described above, the synchronization signal detection section 84 outputs a synchronization signal detection signal, but this signal is also output to the signal monitoring section 88, and the signal monitoring section 88 that receives this signal stops operating. do. The following operation is similar to that described above, and this time, the terminal 10 ₀ acquires the transmission right at time t ₇ and sends out the paging signal E, data, and synchronization signal S.

By the way, while a certain terminal is transmitting data, etc., the terminal may stop transmitting data etc. due to a failure or the like. In that case, the synchronization signal S is not sent out even though the terminal is supposed to send it out. If this state continues, the entire system will become inoperable from then on. In the present invention, in consideration of such a case, a terminal in a state of waiting for a synchronization signal sends out a synchronization signal S. This will be explained below with reference to the time chart of FIG. 3c.

At time _t0 , the terminal ₁₀₀ sends out the synchronization signal S (step 103), and each terminal detects the synchronization signal detection section 8.
5 detects this synchronizing signal S (YES in steps 103 and 104), and the timer setting section 86 sets the timer value T ₁ in the timer 60 at time t ₁ (step 105). The terminal ₁₀₁ acquires the transmission right at time _t2 , which is a time τ elapsed from time _t1 , and since there is data to be transmitted (YES in step 107), it transmits the paging signal E and the data (steps 109 and 111). ).
Assuming that the destination address DA included in the address field in the paging signal E is "4", the terminal ₁₀₄ detects the paging signal E (YES in step 110) and the call signal is addressed to its own terminal (step 110). 113 (YES), so data is received (step
114). On the other hand, the terminals 10 ₀ , 10 ₂ , and 10 ₃ detect the calling signal E (YES in step 110), and since it is not addressed to their own terminal (NO in step 113), the timer setting section 86 sets the timer value T ₂ to the timer 60. (Step 115). Therefore, the terminal 10 ₁ is in the transmitting state, the terminal 10 ₄ is in the receiving state, and the terminals 10 ₀ , 10
₂ and 10 ₃ are waiting for a synchronization signal.

Now, while the terminal 10 ₁ in the transmitting state is transmitting data, the terminals 10 ₀ and 10 in the synchronization signal waiting state
₂ and 10 ₃ , the signal monitoring unit 88 outputs a signal presence signal to the timer setting unit 86, so the timer value T 2 continues to be set in the timer 60, and the timer value T ₂ continues to be set in the timer 60.
0 never times up. However, assume that the terminal ₁₀₀ fails at time _t3 and stops sending data. After that, in the terminals 10 ₀ , 10 ₂ , and 10 ₃ that are waiting for a synchronization signal, the signal monitoring section 88 does not output a signal present signal to the timer setting section 86 . Therefore, in the terminal 10 ₀ , the timer 60 times up at time t ₄ when 5τ has elapsed from time t ₃ (YES in step 117 ), and outputs a time-up signal to the transmission/reception control section 87 . When the transmission/reception control section 87 receives this time-up signal, it acquires the transmission right. Since there is no data to be transmitted (NO in step 120), the transmission/reception control section 87 activates the synchronizing signal transmitting section 82 to transmit the synchronizing signal S (step 103).

Note that in the above embodiment, the data sending terminal is
Immediately after sending the calling signal E, data is sent to the data receiving terminal, but the data receiving terminal receives the response signal A after receiving the calling signal E.
(Includes acknowledgment information ACK, source address SA, destination address DA, and check code BCC.)
The response signal A may be sent to the data sending terminal, and the data sending terminal may send the data to the data receiving terminal after receiving the response signal A. Furthermore, the data length information may be included in the calling signal E, and the data receiving terminal may send out the response signal A again after receiving the data.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, each terminal sets a different timer value in a timer depending on the synchronization signal transmitted by the terminal itself or another terminal, and adjusts the time-up of the timer. Therefore, since the timing at which each terminal acquires the transmission right is controlled by each terminal, conflicts in the transmission right can be prevented. Therefore, there is no need for a master controller, which was a drawback of the conventionally used polling method, and the system can be configured at low cost. Furthermore, even when the number of terminals increases, unnecessary time is not wasted on polling. Furthermore, in the present invention, since all terminals can serve as calling parties, it is possible to transmit dates between terminals. Furthermore, even if a certain terminal fails during data transmission, failure of the entire system can be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a terminal for realizing the transmission control method according to the present invention, FIG. 2 is a flowchart for explaining the operation of the terminal in FIG. 1, and FIG. 4 is a time chart for explaining the operation of the present invention, FIG. 4 is a system configuration diagram showing an example of the configuration of a multi-drop to which the transmission control method according to the present invention is applied using the terminal in FIG. 1, and FIG. The figure is a block diagram of a multi-drop system to which the conventional polling method is applied, and FIG. 6 is a flowchart for explaining the conventional collision detection method. 10 ₀ to 10 ₄ ... terminal, 20 ... serial data bus, 30 ... bus transceiver, 31 ...
P/S converter, 32...S/P converter, 40...
Setting switch, 50... Input/output device, 60... Timer, 70... Memory, 71... Transmission data storage area, 72... Reception data storage area, 80...
...Control device, 81...Terminal number holding unit, 82...
Synchronous signal sending unit, 83... Calling signal sending unit,
84... Synchronization signal detection section, 85... Calling signal detection section, 86... Timer setting section, 87... Transmission/reception control section, 88... Signal monitoring section.

Claims (1)

[Claims] 1 In a so-called multi-drop where multiple terminals are connected to one transmission path, each terminal is assigned a different terminal number, and each terminal has at least a synchronization field containing synchronization information and a field containing its own terminal number. a synchronization signal sending means for sending out a synchronization signal having an address field of 1 to the transmission path, a synchronization signal detection means for detecting the synchronization signal on the transmission path, and a call field including at least call information and sending data. a paging signal transmitting means for transmitting a paging signal having a second address field including a destination terminal number to be sent to the transmission path; a paging signal detection means for detecting the paging signal on the transmission path; and a synchronization signal. A first timer value is set, which is calculated according to a predetermined arithmetic expression from the terminal number included in the first address field of the synchronization signal detected by the detection means and the own terminal number. 1 timer, and a first timer that acquires the first transmission right when the first timer times up if the calling signal detecting means does not detect a calling signal before the first timer times up. a transmission right acquisition means, a signal monitoring means for monitoring whether or not there is a signal on the transmission path, and a destination terminal included in the second address field in the paging signal detected by the paging signal detection means. It is activated when the number does not match the own terminal number, and a second timer value predetermined corresponding to the own terminal number is set each time the signal monitoring means determines that there is a signal on the transmission path. a second timer, and if the synchronization signal detection means does not detect the synchronization signal before the second timer times up, the second timer acquires a second transmission right when the second timer times up. Second to do
When the second or first transmission right is acquired by the transmission right acquisition means and the second or first transmission right acquisition means, if there is no data to be transmitted, the synchronization signal transmission means is activated. and sends a synchronization signal to the transmission path, and if there is data to be sent, first activates the calling signal sending means to send a calling signal and then sends the data to be sent to the transmission path. transmission control means for activating the synchronization signal sending means to sequentially send out synchronization signals after completion of data transmission; and a destination terminal included in the second address field in the calling signal detected by the calling signal detecting means. 1. A transmission control system comprising means for receiving subsequently transmitted data when the number matches the own terminal number.