JPH0439939B2 - - 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 whether there is a request for transmission to each terminal by transmitting an appropriate transmission control code and a terminal number assigned to each terminal to the serial data bus 20 ( poll). On the other hand, the polled terminal returns an end code if there is no transmission request, and transmits data in an appropriate transmission format if there is a transmission request.

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'.

[Problems to be Solved by the Invention] However, the polling method requires a master controller separate from the terminal, which has the disadvantage that the system becomes 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 second timer that is set to a predetermined second timer value if there is no data to be transmitted when the first transmission right acquisition means acquires the first transmission right; , If the synchronization signal detection means does not detect a synchronization signal or the call signal detection means does not detect a calling signal before the second timer times up, a second transmission is performed when the second timer times up. a second transmission right acquisition means for acquiring the right to transmit, a signal monitoring means for monitoring whether or not there is a signal on the transmission path, and the second address in the paging signal detected by the paging signal detection means. It is activated when the destination terminal number included in the field does not match the own terminal number, and every time the signal monitoring means determines that there is a signal on the transmission path, a third a third timer to which a timer value of and transmitting when the third or second transmission right is acquired by the third transmission right acquisition means or the second transmission right acquisition means. If there is no data to be transmitted, the synchronization signal sending means is activated to send a synchronization signal to the transmission path, and the first, second or third transmission acquisition means performs the first, second or third transmission. When the right is acquired, if there is data to be sent, the calling signal sending means is first activated to send the calling signal to the transmission path, and then the data to be sent is sent to the transmission path. a transmission control means for activating a synchronization signal sending means to sequentially send out synchronization signals; and a transmission control means for starting a synchronization signal sending means to sequentially send out synchronization signals, and a transmission control means in which the destination terminal number included in the second address field in the calling signal detected by the calling signal detection means is the own terminal number. [Embodiment] 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 10 _i (0
≦i≦4) means 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. a timer 60 whose value is set;
It has a memory 70 having a program and work area, and a control device 80 consisting of a microprocessor for controlling the bus transceiver 30, input/output device 50, timer 60, and 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 converts parallel data from the control device 80 into serial data and sends it onto the real data bus 20.
Serial converter (hereinafter abbreviated as P/S converter)
31, and 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. There is. 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. 87 is a transmission/reception control section for controlling transmission and reception of signals, 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.
A timer value T ₀ corresponding to the timer 60 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 10 ₀ , 10 ₁ , 10 ₂ , 10 ₃ and 10 ₄ are τ, 2τ, 3τ, 4τ and 5τ, respectively.
becomes.

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 unit 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) x 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, since it is assumed that there is no data to be detected at all terminals, the transmission/reception control unit 87 notifies the timer setting unit 86 to that effect (no data). Upon receiving this, the timer setting section 86 sets a predetermined timer value _T2 in the timer 60 (step 108).

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

T ₂ = W×τ ...(3) On the other hand, other terminals 10 ₂ , 10 ₃ , 10 ₄ and 10 ₀
Also, from time t ₁ to 2τ, 3τ, 4τ and
Since the transmission right is acquired at the time when 5τ has elapsed and there is no data to be sent, the timer value T ₂ is set in the timer 60.

Next, in the terminal ₁₀₁ , the timer 60 times up at time _t3 , which is 5τ after time _t2 (YES in step 109), and the transmission/reception control unit 87 acquires the transmission right as described above. , since there is no data to be sent (NO in step 110), the step
Returning to step 103, 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 _t4 (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.

Figures 3b and 3c show an example where there is data to be sent to the terminal.

First, referring to FIG. 3b, after the power is turned on, a timer value _T0 is set in the timer 60 of each terminal (step 101), and the timer 60 first times up at time _t0 (YES in step 102). Terminal 10 ₀
The synchronization signal sending section 82 sends out the synchronization signal S onto the serial data bus 20 (step 103), and each terminal detects the synchronization signal S in the synchronization signal detection section 84 (YES in steps 103 and 104). , the timer setting unit 86 sets the timer value T ₁ at time t ₁ (step 105).

At time _t2, when time τ has elapsed since time _t1 , the terminal ₁₀
Then, the timer 60 times up (YES in step 106), and the transmission/reception control section 87 acquires the transmission right, but there is no data to be sent (step 106).
107), the timer setting section 86 sets the timer value _T2 in the timer 60 (step 108).

At time _t3 , when time 2τ has elapsed since time _t1 , 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 112). 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 112, step 113)
YES and YES in step 114). Next, terminal 10 ₂
Then, the transmission/reception control section 87 reads out the read/write control signal R/ (high level), and
By sequentially sending addresses from the address line AD, the sending data stored in the sending data storage area 71 continues to be sent until there is no more data to send (steps 115 and 116).
NO). On the other hand, in terminals other than terminal ₁₀₂ , the paging signal detection section 85 first detects the inquiry information ENQ in the paging signal E, and therefore first detects the paging signal detection signal, and then outputs the paging signal E.
Extract the destination address DA included in the address field in
The DA is sent to the transmission/reception control section 87. The transmission/reception control unit 87 receives the received destination address DA.
and the own terminal number N held in the terminal number holding section 81 (step 117). In this example,
Since the destination address DA is "3", the transmission/reception control unit 87 of the terminal ₁₀₃ whose own terminal number N is "3" writes (low level) the read/write control signal R/, and also outputs the address line AD. By sequentially sending out addresses from 1 to 3, the received data that is sent after the call signal E is stored in the received data storage area 72 (step
118).

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 ₃ in the timer 60 at time t ₄ corresponding to the own terminal number N held in the terminal number holding unit 81 ( Step 119). this time
Since _t4 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 _T3 is expressed by the following equation.

T ₂ = (W+N)×τ (4) 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 120) 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 _T3 is set in the timer 60 every time this signal is received.
119). Therefore, once the timer value _T3 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 119→121→122→120→119 is completed. Alternatively, the loop of steps 121→122→120→121 continues.

Now, on terminal ₁₀₂ that is sending data,
Data transmission ends at time _t5 (step 116).
(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,
122 YES and step 123 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 ₆ and sends out the paging signal E, data, and synchronization signal S.

FIG. 3b shows an example in which the terminal acquires the transmission right in step 107 of FIG. 2 and sends data. On the other hand, FIG. 3c shows an example in which the terminal acquires the transmission right in step 110 of FIG. 2 and sends data.

Referring to Figure 3c, the operation up to time _t3 is as follows:
Since this is the same as that shown in FIG. 3a, the explanation of the operation up to that point will be omitted.

In the terminal ₁₀₁ , when the timer 60 time-laps (YES in step 109), the transmission/reception control unit 87 acquires the transmission right and there is data to be sent (YES in step 110), so the call signal E,
Send data and synchronization signal S (step 112,
115, 116 and 103).

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. 3d.

At time _t0 , the terminal ₁₀₀ sends out the synchronization signal S (step 103), and each terminal detects the synchronization signal detection section 8.
4 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 112 and 115). ).
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 113) and the call signal is addressed to its own terminal (step 117 (YES), the data is received (step 118). On the other hand, the terminals 10 ₀ , 10 ₂ , and 10 ₃ detect the calling signal E (NO in step 117), and since it is not addressed to their own terminal (NO in step 117), the timer setting unit 86 sets the timer value T ₃ to the timer 60. (Step 119). 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 3 continues to be set in the timer 60, and the timer value T ₃ 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 121 ), 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 124), 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, data length information may be included in the calling signal E, and the data receiving terminal may send out the response signal A again upon completion of data reception.

〔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 of each terminal's transmission acquisition right is controlled by each terminal, it is possible to prevent transmission rights conflicts. 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, all terminals can serve as calling parties, so data transmission between terminals is possible. 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 is
a synchronization signal sending means for sending out a synchronization signal having at least a synchronization field containing synchronization information and a first address field containing an own terminal number to the transmission path; and a synchronization signal detection device for detecting the synchronization signal on the transmission path. a paging signal transmitting means for transmitting a paging signal to the transmission path, the paging signal having at least a paging field containing paging information and a second address field containing a destination terminal number to which data is to be sent; A call signal detection means for detecting a call signal, and a terminal number included in the first address field in the synchronization signal detected by the synchronization signal detection means and the own terminal number according to a predetermined calculation formula. A first timer is set to the first timer value obtained by a first transmission right acquisition means that acquires the first transmission right when a time-up occurs; a second timer to which a second timer value is set; and if a synchronization signal is not detected by the synchronization signal detection means or a call signal is detected by the call signal detection means before the second timer times out; , a second transmission right acquisition means for acquiring a second transmission right when the second timer times up; a signal monitoring means for monitoring whether or not there is a signal on the transmission path; and a paging signal detection means. It is activated when the destination terminal number included in the second address field in the call signal detected by the means does not match the own terminal number, and the signal monitoring means determines that there is a signal on the transmission path. a third timer in which a predetermined third timer value corresponding to the own terminal number is set for each terminal number; and the synchronization signal is detected by the synchronization signal detection means before the third timer times up. If not, the third timer acquires the third transmission right when the third timer times out.
the third or second transmission right acquisition means; and the third transmission right acquisition means or the second transmission right acquisition means.
If there is no data to be transmitted when the transmission right is acquired, the synchronization signal sending means is activated to send a synchronization signal to the transmission path, and the first, second or third transmission acquisition means When the first, second, or third transmission right is acquired, if there is data to be sent, the calling signal sending means should be activated first to send the calling signal, and then the above calling signal should be sent to the transmission path. The data is transmitted to the transmission control means which activates the synchronization signal transmission means to sequentially transmit the synchronization signals after the transmission of the data is completed, and the second address field in the call signal detected by the call signal detection means. 1. A transmission control system comprising: means for receiving subsequently transmitted data when a destination terminal number included matches the own terminal number.