JP2013175958A - Differential type transmission apparatus and data collision detection method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a differential type transmission apparatus which can more securely detect data collision in a transmission path having a branch.SOLUTION: A differential type transmission apparatus is connected to a transmission path having a branch and is arranged in each node which differentially transmits a serial signal. The differential type transmission apparatus includes: a signal comparison section 90 for comparing signal waveforms of transmission data and reception data and generating a non-matching signal; a maximum detection section 66 for detecting maximum pulse width (Tmax) of the non-matching signal; a serial transmission interface 62 for checking an error of reception data; and a collision determination section 64 for determining data collision of transmission/reception data when the maximum pulse width (Tmax) is reference pulse width (Tj) or more. When the serial transmission interface 62 detects the error, the collision determination section 64 updates the reference pulse width (Tj) to the maximum pulse width(Tmax) when the maximum pulse width (Tmax) is smaller than the reference pulse width (Tj).

Description

  The present invention relates to a differential transmission apparatus, and more particularly to a differential transmission apparatus capable of detecting a data collision even in a transmission line having a branch, and a data collision detection method thereof.

  There is known a multi-type air conditioner in which a plurality of indoor unit units are connected in parallel to one outdoor unit. For signal transmission between each device of this apparatus, a two-wire crossover wiring system using a serial (serial encoded signal) transmission technique is adopted in order to save the line. With this wiring system, it is possible to control a plurality of indoor units / outdoor units with one remote controller.

  Each device (node) such as a remote controller, an indoor unit, and an outdoor unit of the multi-type air conditioner includes a differential transmission device to perform signal transmission. This differential transmission apparatus employs an asynchronous communication system (start / stop synchronous communication). Asynchronous communication system is a serial transmission in which a start bit (STR) is added immediately before 1 byte (8 bits) of character data and a stop bit (STP) is added immediately after the character data. Refers to the method. Although this serial transmission method is synchronized in character data units, the timing of sending each character data may be arbitrary, so it is also called asynchronous. Normally, parity data (1 bit) for error detection is inserted after the character data.

  Furthermore, when each device (node) of the multi-type air conditioner shares one transmission path, each node transmits communication data on the transmission path while monitoring the “vacant” state of the transmission path. For this, CSMA / CD (Carrier Sense Multiple Access with Collision Detection) is used.

  In the conventional serial transmission technology, (1) error detection by a serial reception circuit built in the microcomputer constituting the differential transmission device, and (2) collation of each byte of transmission / reception data is detected. And was done. In error detection (1) above, error detection is performed by a parity check and an H level check of stop bits in the serial reception circuit. However, since the accuracy of such error detection is not necessarily high, data collision may not be detected only by error detection. Further, in the collation of transmitted / received data in (2) above, data collision is detected by causing distortion in the signal waveform of communication data due to data collision. However, since the signal waveform of the communication data may not be distorted in the vicinity of the transmission node, the data collision may not be detected only by the distortion of the signal waveform.

  Further, when the transmission path is a long distance (up to 2000 m), the influence of the DC resistance, the capacitor, and the inductor component of the transmission path is increased. As a result, when the collision partner nodes that started transmission at the same time are electrically located at a long distance (when the resistance value is large), the collision partner nodes may not be able to detect data collision with each other. In this case, since the counterpart node of the transmission destination detects a data collision and discards the data, a response does not return from the transmission destination to the transmission source. In this case, since the transmission source performs the transmission operation again, the transmission line is wasted, and the use efficiency of the transmission line is deteriorated.

  Regarding the above problem, the inventor according to the present application has already confirmed that the pulse width of the mismatch signal output from the comparison circuit that compares the transmission data and the signal that has received the data on the transmission path is such that no data collision occurs. A phenomenon that is short and becomes long when a data collision occurs is found, and the following Patent Document 1 proposes a technique for determining the presence or absence of a data collision based on the pulse width of the mismatch signal.

JP 2011-66722 A

  By the way, in the signal transmission between each device (node) of the multi-type air conditioner, a phenomenon in which the delay time of communication data becomes longer depending on the combination of the number of branches of the transmission path and the transmission path length of each branch is new. Found in FIG. 6 shows the relationship between the number of branches in the transmission path and the delay time of communication data. As shown by curve I in FIG. 6, the delay time of communication data tends to increase as the number of transmission path branches increases. As a result, the pulse width of the mismatch signal changes depending on not only the presence / absence of data collision but also the combination of the number of transmission path branches and the transmission path length of each branch. For this reason, in determining whether or not there is a data collision, simply comparing the pulse width of the mismatch signal with a certain threshold value causes a data collision even though no data collision actually occurs. May be misjudged.

  In a multi-type air conditioner installed in a building such as a building, the number of transmission path branches and the transmission path length of each branch are different for each building. In addition, in the multi-type air conditioner, the number of transmission path branches and the transmission path length of each branch are often changed later by adding, removing, or moving indoor units. For this reason, the pulse width that is the standard of the mismatch signal that is optimal for determining the presence or absence of data collision differs for each multi-type air conditioner, and may change due to the addition of a node or the like.

  Accordingly, an object of the present invention is to provide a differential transmission apparatus and a data collision detection method thereof that can more reliably detect a data collision even in a transmission line having a branch.

  In order to achieve the above object, a differential transmission apparatus according to the present invention is a differential transmission apparatus provided at each of a plurality of nodes connected to a transmission line having a branch and performing differential transmission of serial signals. A signal comparison unit that compares a signal waveform of transmission data transmitted to the transmission path with a signal waveform of reception data received from the transmission path to generate a mismatch signal composed of a pulse train; and a pulse train of the mismatch signal A maximum detector for detecting a maximum pulse width of pulse widths of each of the pulses, a serial reception circuit for detecting an error in the received signal by performing an error check on the received data, and the maximum pulse width being a reference pulse width A collision determination unit that determines that a data collision between the transmission data and the reception data has occurred. The collision determination unit is configured such that the serial reception circuit has an error. In the case when it is detected, or received data in the verification result is a mismatch, and when the maximum pulse width is smaller than the reference pulse width is characterized by updating said reference pulse width to the maximum pulse width.

According to the present invention configured as described above, when the serial reception circuit detects an error or when the collation result of the transmission / reception data does not match, the reference pulse has a maximum pulse width smaller than the reference pulse width. The width is updated to the maximum pulse width. As a result, the reference pulse width for determining the presence or absence of data collision is changed to a more appropriate value. For this reason, a data collision is detected more reliably even in a transmission line having a branch. Moreover, the occurrence of retransmission due to data collision is reduced by reducing false detection of data collision. As a result, the use efficiency of the transmission path is improved and the expected time until the transmission is completed successfully is reduced.
Furthermore, even if the number of branches of the transmission path and the transmission path length of each branch are changed later, a new reference pulse width adapted to the changed transmission path is set. Thereby, even when the transmission path is changed later, the data collision is detected more reliably.

In the present invention, it is preferable that the collision determination unit uses the maximum pulse width as a reference even when the serial reception circuit does not detect an error or when the collation result of the transmission / reception data matches. When the pulse width is greater than or equal to the pulse width, it is determined that the data collision has occurred.
Thereby, a data collision is detected more reliably.

Preferably, in the present invention, when the collision determination unit determines that the data collision has occurred a predetermined number of times, the reference pulse width is updated to the initial reference before being updated to the maximum pulse width. Change to pulse width.
Thereby, generation | occurrence | production of the misdetection by the detection sensitivity of a data collision being too high is suppressed.

In the present invention, it is preferable that the collision determination unit determines whether or not there is a data collision for transmission data within a predetermined number of bytes from the start of transmission of transmission data.
If no data collision occurs within a predetermined number of bytes after transmission data transmission starts, no data collision occurs thereafter. Therefore, by processing transmission data within a predetermined number of bytes after transmission data transmission starts, the processing load on a processing device such as a microcomputer is reduced. As a result, the performance required for a processing apparatus such as a microcomputer is alleviated, and the cost of the processing apparatus can be reduced.

Preferably, in the present invention, when the collision determination unit determines that a data collision has occurred, processing by the maximum detection unit and the collision determination unit is stopped.
As described above, after the data collision is detected, the processing load of the processing device such as the microcomputer is reduced by stopping (invalidating) the processing by the maximum detection unit and the collision determination unit. As a result, the performance required for a processing apparatus such as a microcomputer is alleviated, and the cost of the processing apparatus can be reduced.

  Also, the data collision detection method of the differential transmission device according to the present invention is the data of the differential transmission device provided in each of a plurality of nodes that are connected to a transmission line having branches and perform differential transmission of serial signals. A collision detection method, comprising: comparing a signal waveform of transmission data transmitted to the transmission path with a signal waveform of reception data received from the transmission path to generate a mismatch signal composed of a pulse train; and the mismatch A maximum detection for detecting a maximum pulse width of pulse widths of each pulse of a pulse train of the signal, an error detection process for detecting an error of the reception signal by performing an error check of the reception data in a serial reception circuit, and the maximum A collision determination for determining that a data collision between the transmission data and the reception data occurs when a pulse width is equal to or greater than a reference pulse width; and the serial reception circuit In case of detecting the error, when the maximum pulse width is smaller than the reference pulse width, it is characterized in that it comprises, a updating process for updating the reference pulse width to the maximum pulse width.

According to the present invention configured as described above, when the serial reception circuit detects an error, the reference pulse width is updated to the maximum pulse width when the maximum pulse width is smaller than the reference pulse width. As a result, the reference pulse width for determining the presence or absence of data collision becomes a more appropriate value. For this reason, a data collision is detected more reliably even in a transmission line having a branch. In addition, the occurrence of retransmission due to data collision is reduced by reducing the situation in which data collision cannot be detected (undetectable). As a result, the use efficiency of the transmission path is improved and the expected time until the transmission is completed successfully is reduced.
Furthermore, even when the number of transmission path branches and the transmission path length of each branch are changed, a reference pulse width adapted to the changed transmission path is set. Thereby, even when the transmission path is changed later, the data collision is detected more reliably.

  According to the differential transmission apparatus and the data collision detection method of the present invention, it is possible to more reliably detect a data collision even in a transmission path having a branch.

It is a block diagram which shows the structure of the multi-type air conditioning apparatus to which this invention is applied. It is a block diagram which shows the structure of the differential type | mold transmission apparatus by embodiment of this invention. It is a timing chart which shows received data and a mismatch signal. It is a flowchart which shows the detection process of the maximum value of the pulse width of a mismatch signal. 3 is a flowchart illustrating a data collision detection method of a differential transmission apparatus according to an exemplary embodiment of the present invention. It is a graph which shows the relationship between the number of branches of a transmission line, and the delay time of communication data.

Hereinafter, embodiments of a differential transmission apparatus and a data collision detection method thereof according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a block diagram showing a configuration of a multi-type air conditioner as a device having a plurality of nodes connected to a transmission line having a branch and performing differential transmission of serial signals, to which the present invention is applied. This multi-type air conditioner is composed of indoor units 11 to 16, remote controllers 21 to 26, outdoor units 31 and 32, an air conditioning monitoring panel 41, and transmission paths 1 to 8 connecting them. Each of the transmission lines 1 to 8 is configured by a signal line of a two-line crossover wiring composed of two wirings having a determined polarity.

  The indoor units 11 and 12 and the outdoor unit 31 are connected by the transmission lines 1 and 3 to perform air conditioning operation integrally, and the indoor units 13 to 16 and the outdoor unit 32 are also connected by the transmission lines 2 and 4 to 6 and integrated. It has become air conditioning operation. Each of the indoor units 11 and 12 calculates a necessary air conditioning capability based on a deviation of the room temperature with respect to the set temperature, and always requests the outdoor unit 31 for the necessary air conditioning capability. The request for the air conditioning capability is transmitted as a request signal to the outdoor unit 31 via the transmission paths 1 and 3. The indoor units 13 to 16 also transmit request signals to the outdoor unit 32 via the transmission paths 2 and 4 to 6.

  The air conditioning monitoring panel 41 is connected to transmission paths 1 to 6 between the indoor and outdoor units via transmission paths 7 and 8. For this reason, the air-conditioning monitoring board 41 receives the request signal transmitted from each indoor unit 11-16 to the outdoor unit 31 or 32, and always grasps the required air-conditioning capability of the indoor units 11-16.

  The indoor units 11 to 16, the remote controllers 21 to 26, the outdoor units 31 and 32, and the air conditioning monitoring panel 41 are each provided with a differential transmission device 50. The differential transmission apparatus 50 will be described with reference to FIG. Each differential transmission device 50 includes a microcomputer 60, a line driver / receiver circuit 70, a signal comparison unit 90, and a receiver output selection circuit 95.

  The microcomputer 60 includes a control unit 61, a serial transmission interface 62, a timer 63, a collision determination unit 64, a memory 65, and a maximum detection unit 66. The microcomputer 60 includes a transmission port TxD, a reception port RxD, and general-purpose ports P1, P2, P3, and Px.

  The control unit 61 controls the operations of the serial transmission interface 62, the timer 63, the collision determination unit 64, and the maximum detection unit 66 when the CPU interprets and executes software stored in the memory 65. Specifically, the start and stop of data transmission / reception are controlled via the interface 62. Further, the control unit 61 controls validity / invalidity of collision detection described later. Further, the control unit 61 controls the on / off of the collision flag based on the determination result of the presence / absence of the collision by the collision determination unit 64. The collision flag is stored in the memory 65.

  The serial transmission interface 62 performs an error check on the received data and detects an error in the received signal. In error detection, a parity check of serial data and an H level check of a stop bit (STP) are performed.

  As will be described later, the collision determination unit 65 determines whether or not there is a data collision on the transmission path based on the mismatch signal output from the signal comparison unit 90.

  The line driver / receiver circuit 70 includes a differential line driver / receiver IC 80 and a differential shell line driver / receiver IC 85. The differential line driver / receiver IC 80 includes a differential line driver 81 and a differential line receiver 82. The differential line driver / receiver IC 85 includes a differential line driver 86 and a differential line receiver 87. The outputs of the two differential line drivers 81 and 86 are connected to terminals 1Y and 2Z, 1Z and 2Y having different polarities. The inputs of the two differential line receivers 82 and 87 are connected to terminals 1A and 2B, 1B and 2A having different polarities.

  The differential line drivers 81 and 86 are connected to the transmission port TxD of the microcomputer 60 by the wiring T, and are connected to the transmission line via the transmission port TxD. The data output from the microcomputer 60 is transmitted from the differential line drivers 81 and 86 to the transmission path based on the control signals DE1 and DE2 given from the microcomputer 60 to the differential line drivers 81 and 86. Forwarded to.

  The differential line receivers 82 and 87 are connected to the reception port RxD of the microcomputer 60 by the wiring R, and transfer data to the serial transmission interface 62 via the reception port RxD. The differential line receivers 82 and 87 are connected to the transmission line via the transmission line connection terminal 71.

  When two differential line drivers 81 and 86, two differential line receivers 82 and 87, and the microcomputer 60 transmit / receive data, drivers and receivers belonging to one polarity (for example, The differential line driver 81 and receiver 82) are selected. As the selection (polarity switching) means, control signals DE1, DE2 and CTRL are used.

  A node transmits data according to a predetermined rule. The other node receives the data, determines whether or not the data is correctly received, determines that the connection is reverse polarity if the data is not correctly received, and switches the receiver outputs 1R and 2R according to the control signal CTRL. Thereby, the polarities of all the nodes are determined. At the time of data transmission, the microcomputer 60 selects and uses a driver belonging to the selected polarity by the control signals DE1 and DE2.

  Next, the signal comparison unit 90 will be described. The signal comparison unit 90 compares the signal waveform of the transmission data transmitted to the transmission path with the signal waveform of the reception data received from the transmission path, and generates a mismatch signal composed of a pulse train. The signal comparison unit 90 includes a comparison circuit 91. The comparison circuit 91 is connected to the transmission port TxD of the microcomputer 60 and receives a transmission data signal. The comparison circuit 91 is also connected to the receiver output selection circuit 95 and receives a reception data signal input to the reception port RxD of the microcomputer 60. The comparison circuit 91 is connected to the external interrupt port Px of the microcomputer 60 and transmits the comparison result to the microcomputer 60.

  The comparison circuit 91 compares the signal waveform (transmission waveform) of the transmission data with the signal waveform (reception waveform) of the reception data, and determines the rising / falling position of the transmission waveform and the rising / falling position of the reception waveform. Detecting deviations. The comparison circuit 91 generates a signal (mismatch signal) of a mismatched portion of both waveforms by performing an exclusive OR operation on the positional shift. The comparison circuit 91 is connected to the external interrupt port Px of the microcomputer 60 and transmits the generated mismatch signal to the microcomputer 60.

  FIG. 3 shows received data and a mismatch signal. The upper part of FIG. 3 shows a serial signal for one character input to the reception port RxD of the microcomputer. In this serial signal, a start bit (STR) is added immediately before 1 byte (8 bits) of character data (b0 to b7), and a parity bit (P) and a stop bit (STP) are immediately after the character data. ) Is added.

  The lower part of FIG. 3 shows a mismatch signal. The mismatch signal consists of a pulse train. The pulse width of each pulse of this pulse train corresponds to the difference (time difference) between the rising / falling position of the transmission data signal waveform and the rising / falling position of the reception data signal waveform. Here, pulses with a narrow pulse width are shown before and after the start bit (STR), between b3 and b4 of the character data, and before and after the parity bit (P). Furthermore, a pulse having a wide pulse width is shown in b2 and b6 of the character data.

  Next, the maximum detection unit 66 will be described. The maximum detection unit 66 detects the maximum pulse width of the pulse widths of the pulses in the pulse train of the mismatch signal. In the example shown in FIG. 3, the pulse width of the pulse indicated at the position of bit b2 of the character data is detected as the maximum pulse width (Tmax).

With reference to the flowchart of FIG. 4, the maximum pulse width detection processing by the maximum detection unit 66 will be described.
First, when collision detection is enabled by an external interrupt (INT) (in the case of “yes” in S41), the maximum detector starts detecting the maximum pulse width. When data collision is already detected and collision detection is disabled (stopped) (in the case of “no” in S41), the maximum pulse width detection process is not performed.

  For each pulse of the pulse train of the mismatch signal, while the port level is “Hi” (during “yes” in S42), the duration of “Hi”, that is, the pulse width (Tc) is measured by the timer 63 (S43). ).

  Then, when the pulse port level becomes “Lo” (in the case of “no” in S42), the pulse width of the pulse is determined, and the process proceeds to the next step S45.

  Also, when the pulse width (Tc) exceeds the predetermined upper limit time (Tu) (in the case of “yes” in S44), the process proceeds to the next step S45. This is because when the pulse width (Tc) exceeds the predetermined upper limit time (Tu), it is clear that a data collision has occurred, and the measurement of the pulse width beyond that is useless to the microcomputer. This is because a heavy load is applied. The value of the predetermined upper limit time (Tu) may be set to a length corresponding to a transmission time of 1 bit, for example. Specifically, for example, when the transmission rate is 38,400 bps (bit per sec), about 20 μs (microseconds) may be set.

When the measured pulse width (Tc) is equal to or greater than the maximum pulse width (Tmax) (in the case of “yes” in S34), the value of the maximum pulse width (Tmax) is set to the measured pulse width (Tmax). Tc) is updated (S34). The maximum pulse width (Tmax) is initially set to Tmax = 0 (seconds) at the start of data transfer (at the time of data transmission of the first byte).
In this way, the maximum pulse width of the pulse widths of the pulses of the mismatch signal pulse train is detected.

  Next, the collision determination unit 64 will be described. The collision determination unit 64 determines that a data collision between transmission data and reception data has occurred when the maximum pulse width (Tmax) is equal to or greater than the reference pulse width (Tj). Further, even when the maximum pulse width is smaller than the reference pulse width, the collision determination unit 64 detects the reference pulse width (Tj) when the serial transmission interface 62 detects an error or the collation result of the transmission / reception data does not match. ) Is updated to the maximum pulse width (Tmax) at that time. In order to avoid excessive collision detection, the average of the current reference pulse width (Tj) and the maximum pulse width (Tmax) may be used for updating the reference pulse width (Tj).

A data collision detection method of the differential transmission apparatus according to the embodiment of the present invention will be described with reference to the flowchart of FIG.
When the differential transmission apparatus 50 of a certain node starts data transfer to another node (during data transmission of the first byte), the control unit 61 sends an external interrupt from the signal comparison unit 90 to the microcomputer 60. The operation of the maximum detection unit 66 is permitted through the port Px, and at the same time, the collision detection is enabled. Also, the collision flag indicating the presence or absence of data collision is cleared (“1” remains “0” and “0” remains “0”), and the maximum pulse width (Tmax) is simultaneously decreased to zero.

  The data collision detection process is executed along with data transmission by the differential transmission apparatus 50. However, in the data collision detection processing, when collision detection is effective (“yes” in S501) and the transmission data is within a predetermined number of bytes (for example, 3 bytes) from the start of transmission (“yes” in S502). Only executed). This is because it is not necessary to detect the data collision again when the data collision is already detected and the collision detection processing is disabled, and the data collision within the predetermined number of bytes after the transmission of the transmission data is started. This is because no data collision occurs in principle thereafter. Thereby, the processing load of a processing device such as a microcomputer is reduced.

  Subsequently, the serial transmission interface 62 performs an error check on the received data and detects an error in the received signal. In error detection, a parity check of serial data and an H level check of a stop bit (STP) are performed. If a reception error is detected, or if the collation result of the transmission / reception data does not match (in the case of “yes” in S503), the process proceeds to step S504.

  When the maximum pulse width (Tmax) is smaller than the reference pulse width (Tj) (“yes” in S504), the collision determination unit 64 updates the reference pulse width (Tj) to the maximum pulse width (Tmax) (S505). ). The maximum pulse width (Tmax) is detected by the maximum detector 66 according to the process shown in the flowchart of FIG.

  As described above, even when the maximum pulse width (Tmax) is smaller than the reference pulse width (Tj), the reference pulse width is not detected when the serial reception circuit detects an error or the collation result of the transmission / reception data does not match. As a result of updating to the maximum pulse width, the reference pulse width is changed to a smaller value. Thereby, the reference pulse width for determining the presence or absence of data collision becomes a more appropriate value.

  Subsequently, the control unit 61 invalidates the collision detection (S506). Thereby, the maximum detection part 66 stops. Once it is determined that a data collision has occurred, there is no further benefit in making the determination. For this reason, the maximum detecting unit 66 is stopped to prevent generation of unnecessary load on the microcomputer 60.

  Subsequently, the control unit 61 sets a flag indicating that a data collision has occurred. Here, the collision flag is set to “1” (S507).

  When the collision flag = 1, the control unit 61 interrupts the data transmission in order to avoid the subsequent data collision (S509).

  Subsequently, the control unit 61 transmits dummy data on the transmission path via the transmission port TxD (S510). This dummy data notifies other nodes that a data collision has occurred.

  Further, the control unit 61 waits for data transmission other than dummy data for a predetermined time based on the timer 63 (S511), and then returns to step S501 again to perform a data retransmission operation.

  Even when no reception error is detected (in the case of “no” in S503), the collision determination unit 64 compares the maximum pulse width (Tmax) with the reference pulse width (Tj), Determine presence or absence. When the maximum pulse width (Tmax) is equal to or greater than the reference pulse width (Tj) (Tmax ≧ Tj) (“yes” in S512), the collision determination unit 64 generates a data collision between the transmission data and the reception data. It is determined that Thereby, data collision can be detected more reliably. Then, the process proceeds to step S506 to perform processing at the time of data collision.

  By the way, the reference pulse width (Tj) becomes a smaller value every time it is updated. As a result, the value of the reference pulse width (Tj) may become too small, and the data collision detection sensitivity may become too high. In this case, data retransmission operations frequently occur. Accordingly, when the collision determination unit 64 determines that a data collision has occurred a predetermined number of times (for example, 16 consecutive times), the collision determination unit 64 has updated the reference pulse width (Tj) before being updated to the maximum pulse width (Tmax). The original reference pulse width (Tj) is changed. For example, the initial reference pulse width may be set to a length corresponding to a transmission time of 1 bit. Specifically, for example, when the transmission rate is 38,400 bps, about 20 μs (microseconds) may be set. Thereby, generation | occurrence | production of the misdetection by the detection sensitivity of a data collision being too high is suppressed.

  As described above, according to the present embodiment, even when the maximum pulse width is smaller than the reference pulse width, the reference pulse is detected when the serial transmission interface 62 detects an error or the verification result of the transmission / reception data does not match. The width is updated to the maximum pulse width. As a result, the reference pulse width for determining the presence or absence of data collision becomes a more appropriate value. For this reason, a data collision is detected more reliably even in a transmission line having a branch. Moreover, the occurrence of retransmission due to data collision is reduced by reducing false detection of data collision. As a result, the use efficiency of the transmission path is improved and the expected time until the transmission is completed successfully is reduced. Furthermore, even when the number of transmission path branches and the transmission path length of each branch are changed, a reference pulse width adapted to the changed transmission path is set. Thereby, even when the transmission path is changed later, the data collision is detected more reliably.

  In the above-mentioned embodiment, although the example which comprised this invention on the specific conditions was demonstrated, this invention can perform a various change and combination, and is not limited to this. For example, in the above-described embodiment, the example in which the present invention is applied to the differential transmission device of each device constituting the multi-type air conditioner having a transmission path having a branch has been described. The application target of the device is not limited to the constituent devices of the multi-type air conditioner. The differential transmission device of the present invention may be applied to, for example, a serial signal transmission device connected to a differential transmission line having a branch.

  The present invention is suitable for application to, for example, each device constituting a multi-type air conditioner and a serial signal transmission device.

1 to 8 Transmission path 11 to 16 Indoor unit 21 to 26 Remote control 31, 32 Outdoor unit 41 Air conditioning monitoring panel 50 Differential transmission device 60 Microcomputer 61 Control unit 62 Serial transmission interface 63 Timer 64 Collision determination unit 65 Memory 66 Maximum detection 70 Line driver / receiver circuit 80, 85 Differential line driver / receiver IC
81, 86 Differential line driver 82, 87 Differential line receiver 90 Signal comparison unit 91 Comparison circuit 95 Receiver output selection circuit

Claims (6)

A differential transmission device provided in each of a plurality of nodes connected to a transmission line having branches and performing differential transmission of serial signals,
A signal comparison unit that compares the signal waveform of the transmission data transmitted to the transmission path with the signal waveform of the reception data received from the transmission path, and generates a mismatch signal composed of a pulse train;
A maximum detector for detecting the maximum pulse width of the pulse width of each pulse of the pulse train of the mismatch signal;
A serial receiving circuit that performs an error check on the received data and detects an error in the received signal;
A collision determination unit that determines that a data collision occurs between the transmission data and the reception data when the maximum pulse width is equal to or greater than a reference pulse width, and
The collision determination unit, when the serial reception circuit detects an error or when the verification result of transmission / reception data does not match, when the maximum pulse width is smaller than the reference pulse width, A differential transmission apparatus that is updated to a pulse width. The collision determination unit determines that the data collision has occurred when the maximum pulse width is equal to or larger than a reference pulse width even when the serial reception circuit does not detect an error. The differential transmission apparatus according to claim 1, wherein: When the collision determination unit determines that the data collision has occurred a predetermined number of times, the collision determination unit changes the reference pulse width to an initial reference pulse width before being updated to the maximum pulse width. The differential transmission apparatus according to claim 1 or 2. The differential transmission according to any one of claims 1 to 3, wherein the collision determination unit determines whether or not there is a data collision with respect to transmission data within a predetermined number of bytes from the start of transmission of transmission data. apparatus. The processing according to any one of claims 1 to 4, wherein when the collision determination unit determines that a data collision has occurred, processing by the maximum detection unit and the collision determination unit is stopped. Differential transmission device. A data collision detection method for a differential transmission device provided in each of a plurality of nodes connected to a transmission line having branches and performing differential transmission of serial signals,
Compare the signal waveform of the transmission data transmitted to the transmission path and the signal waveform of the reception data received from the transmission path, and generate a mismatch signal composed of a pulse train,
Maximum detection for detecting the maximum pulse width of the pulse width of each pulse of the pulse train of the mismatch signal;
An error detection process for detecting an error in the received signal by performing an error check on the received data in a serial reception circuit;
A collision determination that determines that a data collision between the transmission data and the reception data occurs when the maximum pulse width is equal to or greater than a reference pulse width;
An update process for updating the reference pulse width to the maximum pulse width when the serial reception circuit detects an error and the maximum pulse width is smaller than the reference pulse width. Data collision detection method for dynamic transmission equipment.

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