JP5374025B2 - Differential transmission equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a differential transmitter which will not misrecognize a transmission path as "free", when it is "busy". <P>SOLUTION: The differential transmitter installed at each of a plurality of nodes performing signal transmission by using a transmission path 5 having two lines of determined polarity comprises a differential line driver 81 connected with the transmission path 5, a differential line receiver 82 connected with the transmission path 5, a serial transmission interface 61 connected with the differential line driver 81 and the differential line receiver 82, a section 63 for detecting the output from the differential line receiver 82 delivered toward the serial transmission interface 61, and a timer 62 operating, based on the detection results from the detecting section 63. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a differential transmission apparatus, and more particularly to a differential transmission apparatus that avoids data collision.

For example, an air conditioner system (air conditioning system) includes a remote controller, an indoor unit, and an outdoor unit. For signal transmission between the devices, a two-wire crossover wiring system using a serial (serial encoded signal) transmission technique is employed in order to save the line. By this method, it is possible to control a plurality of indoor units / outdoor units with one remote controller (Patent Documents 1 and 2).
FIG. 7 is a diagram showing a basic configuration of an air conditioner system using serial transmission and two-wire crossover wiring. As shown in FIG. 7, the remote controller 1 is connected to the indoor units 2a and 2b and the outdoor units 3a and 3b via the transmission path 5, and performs centralized control / monitoring of the air conditioning system. Each of the remote controller 1, the indoor units 2a and 2b, and the outdoor units 3a and 3b (hereinafter sometimes collectively referred to as nodes) includes a differential transmission device. FIG. 8 shows an example of a conventional differential transmission apparatus. The differential transmission apparatus includes a control unit 60, a microcomputer 6 incorporating a serial transmission interface 61 and a timer 62, and a differential line driver / receiver IC 8. The differential line driver / receiver IC 8 includes a differential line driver 81 and a differential line receiver 82. When data is transmitted / received, the microcomputer 6 controls DE and RE, which are control signals of the differential line driver / receiver IC 8.

  The above differential transmission circuit employs a start / stop synchronous communication system. The asynchronous communication system is one of communication protocols, and is a transmission system that transmits a start bit (STR) immediately before character data and a stop bit (STP) immediately after character data. . Therefore, when sending 8-bit character data, at least 10-bit character data is sent. This communication method is a communication method that synchronizes in units of one character. However, since the timing of sending each character may be arbitrary, it is often called an asynchronous method.

When a plurality of nodes (remote controller 1, indoor units 2a and 2b, outdoor units 3a and 3b) share one transmission path 5, communication is performed on the transmission path 5 while monitoring the "free" state of the transmission path 5. Send data. For this, CSMA / CD (Carrier Sense Multiple Access with Collision Detection) is used. The CSMA / CD includes the following steps. Step 1: Before starting communication, it is confirmed whether there is another node that is currently communicating by trying to receive once (Carrier Sense).
Step 2: A plurality of nodes share the same transmission path, and start communication of their own if no other person is communicating (Multiple Access).
Step 3: When a plurality of communications are performed simultaneously, it is detected, and after each node waits for a random time, the transmission procedure is performed again (Collision Detection).
In step 3, since the probability that the same time as the other nodes is spaced is very low, it is possible to avoid another collision.

Japanese Patent No. 2566323 Japanese Patent Laid-Open No. 2-104197

FIG. 9 shows the input (receiver input (differential voltage)) from the transmission line 5 to the differential line receiver 82 and the differential line receiver 82 to the microcomputer 6 (reception port RxD) in the CSMA / CD. FIG. 6 is a diagram illustrating an output (receiver output) to) and an operation of the timer 62 in association with each other.
As shown in FIG. 9, one byte of the receiver output with respect to the receiver input is, for example, a start bit (STR), a data bit (b0 to b7), an error detection bit (PE), and a stop bit (STP). Of 11 bits in total. The timer 62 incorporated as software in the microcomputer 6 is activated (reset in the figure) by receiving a stop bit (STP) and starts counting down. The time from when the timer 62 is activated until the set time elapses (timer up in the figure) is normally set to a time longer than 1 byte (1 byte data transfer time).

As shown in FIG. 9, after the timer 62 is timer-up, no data is transferred from any node to the transmission path 5, and the timer-up state has passed a time of 1 byte or more. To do. Then, there is no data in the transmission line 5, and the microcomputer 6 determines that the transmission line 5 is in the “free” state.
In this state, when data is transmitted from any of the nodes, the differential line receiver 82 of each node that has received the data outputs the data to the reception port RxD of the microcomputer 6. When the microcomputer 6 receives the stop bit (STP) in this data, it starts the timer 62. When the timer 62 operates (timer not up), the microcomputer 6 determines that communication data exists on the transmission path 5 and is “in use”. When it is determined that the transmission line 5 is “in use” in this way, other nodes do not transfer data to the transmission line 5. When the data transfer continues and the stop bit (STP) is received again, the timer 62 starts a new operation. When data transmission is not performed and the timer is up, the microcomputer 6 determines that the transmission path 5 is in an “empty” state. In this state, each node can transmit data onto the transmission path 5.

However, the above-described conventional differential transmission apparatus has the following problems.
As shown in FIG. 10, in the timer-up state, it is assumed that one of the nodes (node A) starts data transmission by determining that the transmission path 5 is “free”. However, since the timer-up state continues until the stop bit (STP) of the data, each node (node B, node C) is transmitted although data is transferred to the transmission path 5. ) Determines that the transmission line 5 is “free”. Therefore, as illustrated in FIG. 10, the node B and the node C transmit data to the transmission path 5.
As described above, since the status monitoring of the transmission line 5 is conventionally performed in units of 1-byte length, in the timer-up state, one of the nodes starts data transmission until the data stop bit (STP). 9 and FIG. 10, the transmission path 5 is mistaken for “vacant” even though the transmission line 5 is “in use”.

  The present invention has been made based on such a technical problem, and an object of the present invention is to provide a differential transmission device that does not misidentify as “empty” when a transmission line is “in use”. .

  For this purpose, the differential transmission apparatus according to the present invention performs signal transmission between a plurality of nodes using a transmission line having two wires of which polarity is determined. In a dynamic transmission device, a differential line driver connected to a transmission line, a differential line receiver connected to the transmission line, a differential line driver and a differential line receiver are connected. A serial transmission interface, and a monitoring unit that determines the presence of data in the transmission path based on a change in voltage of the receiver output output from the differential line receiver to the serial transmission interface. To do.

In the differential transmission device of the present invention, the monitoring unit includes a voltage detection unit that detects a change in the voltage of the receiver output, and a timer that operates when the voltage detection unit detects a change in the voltage of the receiver output. with Ru.
The differential transmission device may include a microcomputer incorporating a serial transmission interface and a monitoring unit. In this case, the receiver output is transferred to the input port of the microcomputer, and the voltage detection unit can detect the receiver output transferred to the input port every predetermined time.
Further, as another aspect, a microcomputer including a serial transmission interface and a monitoring unit is provided, the receiver output is transferred to the external interrupt port of the microcomputer, and the voltage detection unit is the receiver output transferred to the external interrupt port. It is also possible to detect a change in voltage.

  In the above embodiment, a change in the voltage of the receiver output is detected inside the microcomputer. However, a monitoring unit can be provided outside the microcomputer. That is, according to the present invention, the monitoring unit can be arranged between the differential line receiver and the serial transmission interface. The monitoring unit is charged when the receiver output is charged during a high voltage period, and discharged when the receiver output changes from a high voltage to a low voltage. It can be determined that there is data on the road.

  The differential transmission apparatus of the present invention can be used for various applications, but typically can be applied to an air conditioner system. That is, the present invention recommends that a plurality of nodes be a remote controller, an indoor unit, and an outdoor unit that constitute the air conditioner system.

  The differential transmission apparatus of the present invention is provided with a monitoring unit that monitors the state of the receiver output in addition to the serial transmission interface, and this monitoring unit determines the presence state of data in the transmission path based on the voltage change of the receiver output. Since this voltage change changes in bit units, the transmission line can be monitored at an interval shorter than the conventional 1-byte length. Therefore, unlike the conventional case, the transmission path is not mistaken for “vacant” even though the transmission line is “in use”.

<First Embodiment>
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 1 is a block diagram showing a configuration of a differential transmission apparatus according to the present embodiment.
This differential transmission apparatus is applied to the remote controller 1, the indoor units 2a and 2b, and the outdoor units 3a and 3b of the air conditioner system shown in FIG.
The differential transmission apparatus according to the present embodiment includes a microcomputer 6 and a differential line driver / receiver IC 8.
The microcomputer 6 includes a control unit 60, a serial transmission interface 61, a timer 62, and a detection unit 63. The control unit 60 controls the operations of the serial transmission interface 61, the timer 62, and the detection unit 63 when the CPU interprets and executes software stored in a memory (not shown). The timer 62 and the detection unit 63 are realized by software stored in a memory (not shown) included in the microcomputer 6. The microcomputer 6 includes a transmission port TxD, a reception port RxD, and general-purpose ports P1, P2, and Px.

The differential line driver / receiver IC 8 includes a differential line driver 81 and a differential line receiver 82.
The differential line driver 81 is electrically connected to the transmission port TxD of the microcomputer 6 by the wiring T, and receives data transferred from the microcomputer 6 via the transmission port TxD. The differential line driver 81 is connected to the transmission line 5 via the transmission line connection terminal 4. Data received from the microcomputer 6 is transferred from the differential line driver 81 toward the transmission path 5 based on a control signal DE given from the microcomputer 6 to the differential line driver 81. .

  The differential line receiver 82 is electrically connected to the reception port RxD of the microcomputer 6 by the wiring R, and transfers data to the microcomputer 6 via the reception port RxD. The differential line receiver 82 is connected to the transmission line 5 via the transmission line connection terminal 4. Based on the control signal RE applied from the microcomputer 6 to the differential line receiver 82, the differential line receiver 82 receives data via the transmission path 5.

  In the differential transmission apparatus according to the present embodiment, the wiring Rd branched from the wiring R is connected to the general-purpose input port Px. Therefore, the differential transmission apparatus according to the present embodiment can monitor the output state of the differential line receiver 82 in addition to the serial transmission interface 61. The detector 63 samples the voltage change of the data (receiver output) input to the input port Px at high speed. FIG. 2 shows the timing of this sampling and the timing of the operation of the timer 62 by sampling in comparison with the data output from the differential line receiver 82.

FIG. 2 shows that data is not transferred to the transmission line 5 after 1 byte of data is output from the differential line receiver 82 (receiver output).
The receiver output is detected as a voltage at the input port Px. This data is composed of a start bit (STR), data bits (b0 to b7), an error detection bit (PE), and a stop bit (STP). The 1-bit length of this data (data transfer time per bit) is 104 μs. In the receiver output in FIG. 2, a bit corresponding to data “0” is output as a low voltage, and a bit corresponding to data “1” is output as a high voltage.

  The receiver output voltage transferred to the input port Px is sampled at a fixed period. In the present embodiment, the sampling period is 50 μs. In the present invention, the sampling period is not particularly limited. However, if the sampling period is extremely long, the effect of the present invention cannot be obtained. For example, if the sampling period is set to 1 byte or more, the same problem as in the prior art in which a timer is activated for each stop bit occurs. The sampling of the receiver output voltage is preferably performed with a time of 1 bit length or less. In this case, sampling can be performed once per bit. The sampling period of the receiver output voltage is preferably as short as possible, and more preferably, sampling is performed twice per bit for a time of ½ bit length or less. In the present embodiment, the sampling period is set to 50 μs based on this gist.

  In FIG. 2, the input port Px starts receiving data. Until the start of data reception, the receiver output voltage is a high voltage. Since the signal corresponding to the start bit (STR) is “0” in the data, the receiver output voltage is detected as a low voltage. Further, since the signal corresponding to the data “b0” in the data bit is “1” after the start bit (STR) ends, the receiver output voltage is detected as a high voltage. Since the subsequent signals corresponding to “b1” and “b2” are both “0”, the receiver output voltage is detected as a low voltage. Thereafter, the receiver output voltage is sampled in the same manner.

  The timing at which the receiver output voltage is sampled is indicated by ▲ in FIG. In FIG. 2, sampling is performed twice at an interval of 50 μs at the time corresponding to the start bit (STR) after the start of data reception. In this start bit (STR), the receiver output voltage changes from the previous high voltage to the low voltage. Of the two samplings, the receiver output voltage changes from a high voltage to a low voltage during the first sampling. As described above, the timer 62 is activated when it is detected at the time of the preceding sampling and when the voltage is changed. While the timer 62 is in operation, the control unit 60 determines that the transmission path 5 is “in use” and does not issue an instruction to transmit data to the differential line driver 81.

  Even after the transition from the start bit (STR) to the data bit (b0), sampling of the receiver output voltage is performed at intervals of 50 μs. The sampling corresponding to the data bit (b0) is also sampled twice at an interval of 50 μs. In this data bit (b0), the receiver output voltage changes from the previous low voltage to the high voltage. Of the two samplings, the receiver output voltage changes from a low voltage to a high voltage at the first sampling. Therefore, the timer 62 is activated. Therefore, the operation of the timer 62 is continued, and the microcomputer 6 determines that the transmission path 5 is “in use”.

  As described above, the differential transmission apparatus according to this embodiment detects that the receiver output voltage changes from a low voltage to a high voltage by sampling the input port Px. The differential transmission apparatus according to the present embodiment operates the timer 62 every time the detection result is obtained, thereby using the transmission line 5 in a period of less than 1 bit, specifically 1/2 bit. The situation can be monitored. Therefore, as shown in FIG. 2, in the transmission line 5 that has not been used in the previous period, after the use of the transmission line 5 is newly started, in a period corresponding to 1-byte data related to the use. In addition, the control unit 60 can recognize that the transmission path 5 is “in use”. Therefore, the control unit 60 issues a data transfer instruction (DE) to the differential line driver 81 in order to avoid data collision even when there is data to be transferred to the transmission line 5. Absent.

<Second Embodiment>
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. However, since the basic configuration of the second embodiment is the same as that of the first embodiment, differences will be mainly described here.
The differential transmission apparatus according to the second embodiment uses the external interrupt port / INT of the microcomputer 6.

As shown in FIG. 3, in the differential transmission apparatus according to the present embodiment, the wiring Rd branched from the wiring R is connected to the external interrupt port / INT. Therefore, the differential transmission apparatus according to the present embodiment can monitor the output state of the differential line receiver 82 in addition to the serial transmission interface 61. The detection unit 64 detects a voltage change of data input to the external interrupt port / INT.
FIG. 4 shows that data is not transferred to the transmission path 5 after 1 byte of data is output from the differential line receiver 82 (receiver output).
As shown in FIG. 4, in the receiver output, a bit corresponding to data “0” is output as a low voltage, and a bit corresponding to data “1” is output as a high voltage. When the voltage changes from a high voltage to a low voltage, this is input to the external interrupt port / INT as an external interrupt signal.

  In FIG. 4, the external interrupt port / INT starts receiving data. Until the start of data reception, the receiver output voltage is a high voltage. Since the signal corresponding to the start bit (STR) is “0” in the data, the receiver output voltage changes from a high voltage to a low voltage. Further, since the signal corresponding to the data “b0” in the data bit after the start bit (STR) ends is “1”, the receiver output voltage changes to a high voltage. Since the subsequent signals corresponding to “b1” and “b2” are both “0”, the receiver output voltage during this period is a low voltage. Thereafter, the receiver output voltage changes in the same manner.

  As shown in FIG. 4, after the receiver output voltage is changed by the start bit (STR), the data bit (b0) is changed from the start bit (STR) to the data bit (b0). After changing from (b0) to data bit (b1) and changing the receiver output voltage, after changing from data bit (b2) to data bit (b3) and changing the receiver output voltage, each time The timer 62 is activated. From the state of the timer 62, the control unit 60 determines that the transmission line 5 is “in use”.

  As described above, each time the detection unit 64 detects that the receiver output voltage input to the external interrupt port / INT changes from a low voltage to a high voltage, the timer 62 is activated, so that the present embodiment The differential transmission apparatus can grasp the usage status of the transmission path 5 in a period of less than 1 bit length. Therefore, as shown in FIG. 4, in the transmission line 5 that has not been used in the previous period, after a new use of the transmission line 5 is started, in a period corresponding to 1-byte data related to the use. In addition, the control unit 60 can determine that the transmission path 5 is “in use”. Therefore, the control unit 60 issues a data transfer instruction (DE) to the differential line driver 81 in order to avoid data collision even when there is data to be transferred to the transmission line 5. Absent.

<Third Embodiment>
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS. However, since the basic configuration of the third embodiment is the same as that of the first and second embodiments, differences will be mainly described here.
The differential transmission apparatus according to the third embodiment is provided with a circuit for detecting the state of the transmission path 5 outside the microcomputer 6.

  As shown in FIG. 5, in the differential transmission apparatus according to the present embodiment, a wiring Rd branched from the wiring R is connected to a general-purpose input port Px. The monitoring unit 9 is disposed on the branched wiring Rd. The monitoring unit 9 includes a charging / discharging circuit, and charging / discharging is performed according to a change in the receiver output voltage. That is, every time the receiver output voltage changes, the charge / discharge circuit discharges. At times other than this discharge, the charge / discharge circuit is charged. If the charging voltage of the charging / discharging circuit is equal to or higher than the threshold value, the transmission path 5 is determined to be “vacant”, and if the charging voltage of the charging / discharging circuit is less than the threshold value, the transmission path 5 is determined to be “in use”. .

FIG. 6 assumes that data is not transferred to the transmission path 5 after 1 byte of data is output from the differential line receiver 82 (receiver output).
As shown in FIG. 6, the receiver output outputs a bit corresponding to data “0” as a low voltage, and outputs a bit corresponding to data “1” as a high voltage. When the voltage changes from a high voltage to a low voltage, the charge / discharge circuit of the monitoring unit 9 is discharged.

  In FIG. 6, the receiver output voltage is a high voltage until the monitoring unit 9 receives data. Since the signal corresponding to the start bit (STR) is “0” in the data, the receiver output voltage changes from a high voltage to a low voltage as data reception starts. Further, since the signal corresponding to the data “b0” in the data bit after the start bit (STR) ends is “1”, the receiver output voltage changes to a high voltage. Since the subsequent signals corresponding to “b1” and “b2” are both “0”, the receiver output voltage during this period is a low voltage. Thereafter, the receiver output voltage changes in the same manner.

  As described above, every time the receiver output voltage changes, the charge / discharge circuit of the monitoring unit 9 is discharged and the voltage drops. After the voltage drops, the charge / discharge circuit is charged and the charge voltage rises. Thus, the charging voltage of the charging / discharging circuit changes as the receiver output voltage changes. Therefore, the use state of the transmission line 5 can be grasped by detecting the charging voltage of the charging / discharging circuit. That is, the monitoring unit 9 determines that the transmission line 5 is “empty” if the charging voltage of the charging / discharging circuit is equal to or higher than the threshold value, and if the charging voltage of the charging / discharging circuit is less than the threshold value, the transmission line 5 is Judged as “in use”. The determination result is notified to the control unit 60 via the input port Px.

  As described above, the differential transmission apparatus according to the present embodiment has the transmission line 5 according to the charging voltage of the charging / discharging circuit whose charging voltage changes with the change of the receiver output voltage and in a period of less than 1 bit length. It is possible to grasp the usage status. Therefore, as shown in FIG. 6, in the transmission line 5 that has not been used in the previous period, after the transmission line 5 is newly used, in a period corresponding to 1-byte data related to the use. In addition, the control unit 60 can recognize that the transmission path 5 is “in use”. Therefore, the control unit 60 issues a data transfer instruction (DE) to the differential line driver 81 in order to avoid data collision even when there is data to be transferred to the transmission line 5. Absent.

It is a block diagram which shows the structure of the differential type | mold transmission apparatus in 1st Embodiment. It is a figure which shows the operation | movement waveform by the differential type transmission apparatus in 1st Embodiment. It is a block diagram which shows the structure of the differential type | mold transmission apparatus in 2nd Embodiment. It is a figure which shows the operation | movement waveform by the differential type transmission apparatus in 2nd Embodiment. It is a block diagram which shows the structure of the differential type | mold transmission apparatus in 3rd Embodiment. It is a figure which shows the operation | movement waveform by the differential type transmission apparatus in 3rd Embodiment. It is a figure which shows the basic composition of an air conditioner system. It is a block diagram which shows the structure of the conventional differential transmission apparatus. It is a figure which shows the operation | movement waveform by the conventional differential transmission apparatus. It is a figure which shows the operation | movement waveform by the conventional differential transmission apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Remote control, 2a, 2b ... Indoor unit, 3a, 3b ... Outdoor unit, 4 ... Transmission path connection terminal, 5 ... Transmission path, 6 ... Microcomputer, 60 ... Control part, 61 ... Serial transmission interface, 62 ... Timer, 63, 64 ... detection unit, 8 ... differential line driver / receiver IC, 81 ... differential line driver, 82 ... differential line receiver, 9 ... monitoring unit

Claims (5)

In the differential transmission apparatus installed in each node, wherein signal transmission between a plurality of nodes is performed using a transmission line having two wires of which polarity is determined,
A differential line driver connected to the transmission line;
A differential line receiver connected to the transmission line;
A serial transmission interface connected to the differential line driver and the differential line receiver;
A monitoring unit that determines the presence state of data in the transmission line based on a voltage change of a receiver output that is output from the differential line receiver toward the serial transmission interface;
Equipped with a,
The monitoring unit
A voltage detector for detecting a voltage change of the receiver output;
Differential transmission system according to claim Rukoto and a timer activated when detecting that the voltage detecting unit is a change in the voltage of the receiver output. A microcomputer incorporating the serial transmission interface and the monitoring unit;
The receiver output is transferred to an input port of the microcomputer,
The differential transmission apparatus according to claim 1 , wherein the voltage detection unit detects the voltage of the receiver output transferred to the input port every predetermined time. A microcomputer incorporating the serial transmission interface and the monitoring unit;
The receiver output is forwarded to an external interrupt port of the microcomputer;
The differential transmission device according to claim 1 , wherein the voltage detection unit detects a change in the voltage of the receiver output transferred to the external interrupt port. In the differential transmission apparatus installed in each node, wherein signal transmission between a plurality of nodes is performed using a transmission line having two wires of which polarity is determined,
A differential line driver connected to the transmission line;
A differential line receiver connected to the transmission line;
A serial transmission interface connected to the differential line driver and the differential line receiver;
A monitoring unit that determines the presence state of data in the transmission line based on a voltage change of a receiver output that is output from the differential line receiver toward the serial transmission interface;
With
The monitoring unit is disposed between the differential line receiver and the serial transmission interface; and
The receiver output is charged during a high voltage period and discharged when the receiver output changes from a high voltage to a low voltage,
When the charging voltage in the monitoring unit is equal to or lower than a predetermined value, it is determined that the data is present in the transmission path. The differential transmission apparatus according to any one of claims 1 to 4 , wherein the plurality of nodes are a remote controller, an indoor unit, and an outdoor unit that form an air conditioner system.

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