JP4280140B2 - Communication system, electronic equipment - Google Patents

Description

  The present invention relates to a slave device that is daisy chain connected to each other based on, for example, the RS-232C transmission method, a communication system that performs serial communication between host devices, and an electronic device.

  2. Description of the Related Art Conventionally, as a device for detecting a relative movement position in a movable part such as a machine tool or a semiconductor manufacturing apparatus, a displacement detection device that detects a measurement value as an electric signal by an optical or magnetic detection means is known. In particular, there is also a measurement system that can realize a multi-faceted shape analysis by disposing a plurality of such displacement detection devices on a desired measurement object and collecting and processing measurement data acquired from each displacement detection device. It has been proposed (see, for example, Patent Documents 1 and 2). In such a case, usually, the measurement data is accumulated in a host device connected to each displacement detection device via an RS-232C cable and analyzed.

  Incidentally, this RS-232C transmission system is basically one-to-one communication. For this reason, when communicating between a plurality of displacement detection devices, it has been necessary to realize this based on the following method.

  FIG. 5 shows a conventional measurement system 6 in which a multiplexer (switcher) 62 is introduced between the units 63_1 to 63_n in the host device 61 and the displacement detector 63. The measurement data obtained for each of the units 63_1 to 63_n is transferred to the host device 61 via the multiplexer 62 under the RS-232C transmission method. In this measurement system 6, each unit 63_1 to 63_n only needs to have a communication function based on the normal RS-232C transmission method, and no significant system change is required. The increase in cost due to the above cannot be avoided, and a time loss at the time of switching occurs, so that the speed of the entire system cannot be increased.

  Incidentally, as a development of the measurement system 6, a method in which the host device 61 has a plurality of RS-232C communication functions and the switch 62 itself is built in the host device 61, or each of the units 63_1 to 63_n has a switch A method for implementing 62 functions has been devised, but none of them has solved the above-mentioned problems.

  FIG. 6 shows a conventional measurement system 7 using an RS-485 transmission method capable of 1-to-N communication. In this measurement system 7, a signal converter 72 connected to the host device 71 via an RS-232C cable, and an RS-485 cable is used to realize RS-485 communication with the signal converter 72. N signal converters 73_1 to 73_n connected to each other, and units 74_1 to 74_n in the displacement detection device 74 connected to the signal converters 73_1 to 73_n via RS-232C cables are provided. The measurement data obtained for each of the units 74_1 to 74_n is transmitted to the signal converters 73_1 to 73_n under the RS-232C transmission method, and further transferred to the signal converter 72 under the RS-485 transmission method. Each measurement data transferred to the signal converter 72 is further transferred to the host device 71 under the RS-232C transmission method.

  In this measurement system 7 as well, each unit 74_1 to 74_n only needs to have a communication function based on the normal RS-232C transmission method, and no significant system change is required. Since it is necessary to dispose the converters 73_1 to 73_n, there is a drawback that an increase in cost cannot be avoided.

  Incidentally, as a development of this measurement system 7, the host device 71 has an RS-485 communication function and the signal converter 72 itself is built in the host device 71, or the units 74_1 to 74_n have RS-485 communication. Although a method of providing a function has been devised, none of them has solved the above-mentioned problems, and there is a new problem that compatibility with devices adopting the RS-232C transmission method cannot be achieved. To occur.

  FIG. 7 shows a conventional measurement system 8 in which each of the units 74_1 to 74_n in the displacement detector 74 has a link communication function in addition to the RS-232C communication function.

  In this measurement system 8, each RS-232C cable is connected to the master unit 82 connected to the host device 81 via the RS-232C cable and the signal converter 82 in order to realize RS-232C communication. The connected master unit 82 and the units 83_1 to 83_n in the displacement detection device 83 that are daisy-chain connected in order from the master unit 82 are provided.

  Although this measurement system 8 is most frequently used in the past, each unit 83_1 to 83_n must be separately provided with a link communication function in addition to a normal RS-232C communication function. Will increase. In addition, the master unit 82 needs to have a function of relaying between the host device 81 and the displacement detection device 83. Compared with normal RS-232C communication, the burden on the circuit and software increases, and prompt data communication is possible. There is also a problem that it cannot be realized.

Japanese Patent Laid-Open No. 11-120474 JP 11-125545 A

  Therefore, the present invention has been devised in view of the above-described problems, for example, a slave device that is daisy chain connected to each other based on the RS-232C transmission method, a communication system that performs serial communication between host devices, In addition, in an electronic device, it is an object of the present invention to particularly reduce costs by reducing the burden on the master unit as described above and making it an extremely simple communication system.

A communication system to which the present invention is applied is a communication system in which at least one slave device is connected in a daisy chain between the lowest slave device located at the end and the host device, and the host device is connected A slave device that transmits a slave control signal to the slave device and is connected between the host device and the lowest slave device is an upper slave device connected between the slave device and the host device or In response to the slave control signal received from the host device via the first control terminal, at least data generated in the slave device is transmitted to the host slave device or the host device that is the transmission source of the slave control signal . Control means for transferring and generating a first logic signal based on the data transfer status; and Over Bed control signal and the first logical product calculation means and the first of the slave a logical product calculated by the logic calculation means for calculating a logical product of the first logic signal generated by said control means as a slave control signal for the lower slave devices connected to the lower side of the device, transmitting means for transmitting to the front Symbol lower slave device, transmitted from the lower slave device connected to the least significant slave device side of the slave device Second logical product calculating means for calculating a logical product of the slave control signal thus generated and the second logical signal generated by the control means, wherein the control means receives a second logical product from the lower slave device. In response to the slave control signal received via the control terminal, at least the data generated in the slave device is transferred to the upper slave device or host device. And generating the second logic signal based on the data transfer status, and further, when the transfer of the data to the upper slave device or the host device is completed, the first logic signal corresponding to the data transfer status is generated. Generating a logical signal, and the transmission means transmits the logical product calculated by the second logical product calculation means to the upper slave device or host device as a slave control signal for the upper slave device or host device, In the case of outputting data to the upper slave device or the host device connected between the slave device and the host device, the logical product calculated by the first logical product calculation means is sent to the lower slave device. For the slave control signal indicating to prohibit the transfer of data to the lower slave device, when the data transfer is completed, When the logical product calculated by the first logical product calculating means is transmitted to the lower slave device as a slave control signal indicating that data transfer is permitted to the lower slave device, and the data transfer is completed. to, when receiving the slave control signal indicating that the slave device there for transmitting data in a lower slave device, is a priority to the output of the data so as to move the lower slave device, to a higher-level The data is transferred by serial communication in a state in which priority is given to the output of the data to a slave device .

An electronic device to which the present invention is applied is an electronic device connected in a daisy chain between the lowest slave device located at the end and the host device, and the upper device connected between the electronic device and the host device. In accordance with a slave control signal received from the slave device or the host device via the first control terminal, at least data generated in the electronic device is a higher-level slave device that is a transmission source of the slave control signal or Control means for transferring to the host device and generating a first logic signal based on the data transfer status, and a logical product of the slave control signal and the first logic signal generated by the control means first aND calculation means and the least significant slave device than the electronic device a logical product calculated by the first logic calculating means for calculating the As a slave control signal for the connected subordinate slaves, the transmission means and the slave control signal transmitted from the lower slave device than the electronic apparatus connected to the least significant slave device side to be transmitted to the front Symbol lower slave device And second logical product calculating means for calculating a logical product with the second logical signal generated by the control means, wherein the control means is connected to the lower slave device via a second control terminal. In response to the received slave control signal, at least the data generated in the electronic device is transferred to the host slave device or the host device, and the second logic signal is generated based on the data transfer status. Further, when the transfer of the data to the upper slave device or the host device is completed, a first logic signal corresponding to the data transfer status is generated. The transmission means transmits the logical product calculated by the second logical product calculation means to the upper slave device or host device as a slave control signal for the upper slave device or host device, and the control means includes: In the case of outputting data to the upper slave device or the host device connected between the electronic device and the host device, the logical product calculated by the first logical product calculation means is sent to the lower slave device. When the data transfer is completed, the logical product calculated by the first logical product calculation means is transmitted to the lower slave device as a slave control signal indicating that data transfer is prohibited. Sends data to the slave slave device as a slave control signal indicating that the device is allowed to transfer data, and transfers the data. There when completed, when receiving the slave control signal indicating that the slave device there for transmitting data in a lower slave device, so as to transfer the priority to output the data to a lower slave device, and more The data is transferred by serial communication in a state where priority is given to the output of the data to a higher order slave device .

  In communication systems and electronic devices to which the present invention is applied, priority is given to the upper slave device by calculating the logical product of the control signal from the upper slave device or host device and the control signal generated based on the data transfer status. The right to use the transmission line can be given automatically, and interference of link communication between slave devices can be prevented with a simple configuration, and as a result, the cost can be greatly reduced by using an extremely simple system configuration. Is possible.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The communication system 1 to which the present invention is applied includes, for example, as shown in FIG. 1, slave devices 12_1 to 12_n that acquire data from length measuring units 13_1 to 13_n arranged at a plurality of locations with respect to a desired measurement target; The host device 15 for controlling each of the slave devices 12_1 to 12_n is daisy chain connected via a network cable based on, for example, an RS (Recommended Standard) -232C transmission method.

  The length measuring units 13_1 to 13_n are devices for detecting a relative movement position in a movable part such as a machine tool or a semiconductor manufacturing apparatus. For example, a gauge or a scale for detecting a measurement value as an electric signal by an optical or magnetic detection means. And an encoder. Incidentally, the length measurement units 13_1 to 13_n may be sensors that measure temperature, humidity, stress, light quantity, etc., and convert them into electrical signals. Each electrical signal detected by the length measuring units 13_1 to 13_n is supplied to each connected slave device 12_1 to 12_n.

  The slave devices 12_1 to 12_n convert the electrical signals supplied from the length measuring units 13_1 to 13_n into data, and transmit the data to the host device 15 and the like. The slave device 12_1 is daisy chained between the host device and the slave device 12_2. The slave device 12_2 is daisy chained between the slave device 12_1 and the slave device 12_2. That is, one end of each slave device 12 is connected to the host device 15 or a slave device 12 that is closer to the host device 15 among the adjacent slave devices 12 (hereinafter, this slave device 12 is referred to as an upper slave device). The other end of the adjacent slave device 12 is connected to a slave device 12 that is remote from the host device 15 than the host device 15 (hereinafter, this slave device 12 is referred to as a lower slave device).

  When each slave device 12 transmits data TXD based on the electrical signal from the length measurement unit 13 to the host device 15, first, it transmits this to the connected upper slave device. The higher order slave device to which the data TXD is transmitted transmits this to the higher level slave device 12 and sequentially transmits it to the host device 15. Each slave device 12 realizes communication of the data TXD between the lower slave device and the host device 15 by transferring the data TXD from the lower slave device to the upper slave device as it is. Is possible.

  The slave devices 12_1 to 12_n receive data RXD from the host device 15. Even in such a case, the data RXD is transmitted to each slave device 12 via the upper slave device. Further, regarding the data RXD transmitted to the lower slave device, the data RXD can be communicated between the lower slave device and the host device 15 by passing the data RXD directly to the lower slave device.

  Further, the slave devices 12_1 to 12_n allow a control signal ESO for permitting or suppressing transmission / reception of data to / from a lower slave and a control signal EEO including control information for the upper slave or the host device 15. Send. Details of the configuration of the slave device 12 will be described later. The slave device 12 may have a length measuring function by integrating the length measuring unit 13 described above.

  The host device 15 is configured by an electronic device such as a personal computer (PC), for example, records data transmitted from the slave device 12, and displays the recorded data to a user via a display (not shown). In addition, when requested by the user to display desired data, the host device 15 controls to select the optimum data from the recorded data and display it. The host device 15 also serves as a so-called central control device for controlling the entire communication system 1 and supplies a control signal CTS for permitting or suppressing transmission / reception of data to each slave device 12.

  Incidentally, in each of the slave devices 12_1 to 12_n described above, the description is limited to the interface unit. However, in an actual circuit, signals input / output between the internal circuits of the slave device 12 and the RS-232C transmission scheme are used. The signal level is different. Therefore, a predetermined driver circuit may be provided at the input / output terminals of the slave devices 12_1 to 12_n.

  Next, the configuration of the slave device 12 will be described in detail with reference to FIG. 2 taking the slave devices 12_1 and 12_2 as an example.

  The slave device 12_1 includes an MPU (Micro Processing Unit) 21_1, a transmission control unit 22_1 connected to the MPU 21_1, a first AND circuit 31_1, a second AND circuit 32_1, a third AND circuit 33_1, 4 AND circuit 34_1. The slave device 12_2 includes an MPU (Micro Processing Unit) 21_2, a transmission control unit 22_2 connected to the MPU 21_2, a first AND circuit 31_2, a second AND circuit 32_2, a third AND circuit 33_2, And a fourth AND circuit 34_2.

  The MPU 21 is a central processing unit that controls the entire slave device 12, and includes a ROM for storing a control program to be executed, a DRAM as a work area used for data accumulation, development, and the like via a data bus (not shown). Connected. The MPU 21 is supplied with an electrical signal from the length measurement unit 12 and converts it into data.

  Each MPU 21_n includes a TXD output terminal 41_n for outputting data TXD, an RXD input terminal 42_n for inputting data RXD, and an RTS output terminal 43_n for outputting a control signal RTS for the host device 15. A CTS input terminal 44_1 for receiving a control signal CTS transmitted from the host device 15, an ESO output terminal 45_n for outputting a control signal ESO, an EEO output terminal 46_n for outputting an EEO control signal, An EEO input terminal 47_n for inputting an EEO control signal and a TXD input terminal 48_n for inputting data TXD from a lower slave device are provided.

  The first AND circuit 31_1 calculates a logical product of the control signal CTS transmitted from the host device 15 and the control signal ESO output from the MPU 21_1 via the ESO output terminal 45_1. The second AND circuit 32_1 includes a control signal RTS output from the MPU 21_1 via the RTS output terminal 43_1 and a control signal RTS output from the second slave device 12_2 via the second AND circuit 32_2. Calculate the logical product. Further, the third AND circuit 33_1 performs a logical product of the control signal EEO output from the MPU 21_1 via the EEO output terminal 46_1 and the control signal EEO output from the slave device 12_2 via the third AND circuit 33_2. calculate. The fourth AND circuit 34_1 calculates the logical product of the data TXD output from the MPU 21_1 via the TXD output terminal 41_1 and the data TXD output from the slave device 12_2 via the fourth AND circuit 34_2. . Each calculated logical product is subjected to timing control by the transmission control unit 22_1 and transmitted to the host device 15 and the slave device 12_2.

  Similarly, the first AND circuit 31_2 calculates a logical product of the control signal ESO (CTS) transmitted from the slave device 12_1 and the control signal ESO output from the MPU 21_2 via the ESO output terminal 45_2. The second AND circuit 32_2 calculates a logical product of the control signal RTS output from the MPU 21_2 via the RTS output terminal 43_2 and the control signal RTS output from the lower slave device. The third AND circuit 33_2 calculates the logical product of the control signal EEO output from the MPU 21_2 via the EEO output terminal 46_2 and the control signal EEO output from the lower slave device. The fourth AND circuit 34_2 calculates a logical product of the data TXD output from the MPU 21_2 and the data TXD output from the lower slave device via the TXD output terminal 41_2. Each calculated logical product is subjected to timing control by the transmission control unit 22_2 and transmitted to the slave device 12_1 and the lower slave device.

  In such a communication system 1, the MPU 21 that controls each slave device 12 transmits and receives data RXD and TXD based on a control signal ESO (CTS) and a control signal EEO transmitted from the outside.

  That is, in the communication system 1 to which the present invention is applied, in addition to a system for transmitting and receiving data under a normal daisy chain connection, the MPU 21 further inputs / outputs a control signal ESO (CTS) and a control signal EEO. It is essential to newly allocate the terminals 43_n to 47_n.

  Incidentally, the control signals ESO and EEO are obtained by arranging the control signals CTS and RTS, respectively. The control signal CTS is output from the host device 15 which is the highest level of the communication system to the lower slave device 12, whereas the EEO signal is output from the lower slave device to the upper slave device.

  Each slave device 12 prohibits the output of each data TXD from itself when the control signal CTS and the control signal ESO transmitted from the host device 15 or the upper slave device are prohibited (in the case of Low). That is, the slave device 12 that has received the control signals CTS and ESO indicating such prohibition enters an output waiting state even if there is data TXD that the host device 15 or the upper slave device desires to output. Each slave device 12 is prohibited from inputting data from the outside when the control signal EEO transmitted from the lower slave device indicates “prohibited” (in the case of Low). That is, even if there is data TXD, RXD desired to be output to the host device 15 or another slave device 12, the output wait state is entered.

  Next, specific operations in the communication system 1 to which the present invention is applied will be described in more detail.

  Since the TXD transmission line as the transmission line described above is used in common among the slave devices 12, if the plurality of slave devices 12 output data at the same time, interference occurs. Therefore, in the communication system 1 to which the present invention is applied, The slave device 12 closer to the host device 15, in other words, the slave device 12 at a higher level is given priority in data output. When there is a slave device 12 that is executing data communication, data output from other slave devices 12 is prohibited. Each slave device 12 can output data when the transmitted control signal ESO is not “prohibited” (when “communication is possible”).

  For example, when the control signal CTS transmitted from the host device 15 to the slave device 12_1 is prohibited, the slave device 12_1 cannot output data, of course, via the control signal CTS and the MPU 21_1 via the ESO output terminal 45_1. Since the logical product with the control signal ESO output at this time is always Low, the prohibited ESO signal is transmitted to the slave device 12_2 corresponding to the lower slave device. Similarly, in the slave device 12_2 that has received the ESO signal in the prohibited state, the logical product output from the first AND circuit 31_2 is Low. That is, when the control signal CTS transmitted from the host device 15 to the slave device 12_1 is prohibited, data output is prohibited for all the slave devices 12 in the lower order.

  On the other hand, when the control signal ESO transmitted from the host device 15 to the slave device 12_1 indicates “communication enabled” (in the case of High), the right to use the transmission line is transferred to the slave device 12_1, and the data is transferred. It can be output.

  Here, if the slave device 12_1 transmits the data TXD to the host device 15 via the TXD output terminal 41_1, the slave device 12_1 indicates “prohibited” in order to prevent interference with data output from the lower slave. The ESO signal is output from the MPU 21_1 through the ESO output terminal 45_1. As a result, the logical product calculated in the first AND circuit 31_1 becomes Low, and data output can be prohibited for all the slave devices 12 in the lower order. Further, when the output of the data TXD is ended, the slave device 12_1 may transfer the right to use the transmission line to the lower slave by setting the ESO signal to “communicable”.

  On the other hand, if the slave device 12_1 does not transmit the data TXD to the host device 15 via the TXD output terminal 41_1, the use right for transmission is transferred to the lower slave. In such a case, an ESO signal indicating “communication is possible” is output from the MPU 21_1 via the ESO output terminal 45_1. As a result, the logical product calculated in the first AND circuit 31_1 becomes High, and the slave device 12_2 at the lower level can communicate with the host device 15.

  That is, the lower slave device can perform data communication only when receiving the control signal ESO issued after the data communication of the upper slave device is completed, or when all the upper slave devices do not perform data communication. .

  As described above in detail, the slave device 12 calculates the logical product of the control signals CTS, ESO from the upper slave device or the host device 15 and the control signal ESO generated based on the data transfer status. Therefore, it is possible to preferentially give the right to use the transmission line from the upper slave, and it is possible to prevent the interference of link communication between slave devices with a simple configuration. It is possible to achieve a significant cost reduction.

  In particular, each slave device 12 may identify the control signal ESO instead of identifying the control signal CTS, and identify the control signal EEO instead of identifying the control signal RTS, so that the burden does not increase. . That is, it is only necessary to check the control signals ESO and EEO when processing the control signals RTS and CTS in the case of a one-to-one connection. As a result, the slave device 12 can perform communication in the same manner as the one-to-one connection without particularly increasing the burden.

  Further, by capturing the edge where the control signal ESO is generated and outputting it to the adjacent slave device 12, it is possible to reduce the time loss between the slave devices that has occurred in the conventional link communication, and consequently the link communication time. Can be greatly shortened.

  Incidentally, the slave device (hereinafter referred to as the lowest slave device) at the end of the daisy chain connection is in a waiting state until all data communication of the upper slave device is completed. Meanwhile, the lowest slave device transmits an EEO signal to the higher slave device. The upper slave device that has received this EEO signal calculates the logical product of the EEO signal output by itself and transmits it to the upper slave device.

  If the slave device 12_2 receives the control signal EEO from the lower slave device, the control signal EEO is supplied to the third AND circuit 33_2. The third AND circuit 33_2 is also supplied with a control signal EEO supplied from the MPU 21_2 via the EEO output terminal 46_2, and a logical product is calculated between them.

  If an EEO signal indicating “prohibited” is supplied from the lower slave device to the third AND circuit 33_2, the logical product output from the third AND circuit 33_2 becomes Low. On the other hand, when an EEO signal indicating “communication is possible” is supplied from the lower slave device to the third AND circuit 33_2, the control signal EEO is supplied from the MPU 21_2 via the EEO output terminal 46_2. The logical product output from the third AND circuit 33_2 is Low or High. Further, the EEO signal from the lower slave device is supplied to the MPU 21_2 via the EEO input terminal 47_2.

  The MPU 21_2 controls data input / output based on the received EEO signal. In such a case, the MPU 21_2 identifies Low or High when the control signal EEO is received while the data transmitted by the MPU 21_2 is in a state. Further, when the control signal EEO identified by the MPU 21_2 is Low, it indicates that there is at least one lower slave device that desires to transmit data to the host device 15, and the transmission line should be opened. , Prohibit their own data communication. At this time, the MPU 21_2 may generate an EEO signal corresponding to the transfer state and transmit it to the third AND circuit 33_2.

  Incidentally, the control signal EEO including the logical product output from the third AND circuit 33_2 is supplied to the first AND circuit 33_1 and the MPU 21_1 in the slave device 12_1. If an EEO signal indicating “prohibition” is supplied from the third AND circuit 33_2 to the third AND circuit 33_1, the logical product output from the first AND circuit 33_2 becomes Low. On the other hand, when an EEO signal indicating “communication is possible” is supplied from the third AND circuit 33_2 to the third AND circuit 33_1, the control signal EEO supplied from the MPU 21_1 via the EEO output terminal 46_1 is used. Accordingly, the logical product output from the third AND circuit 33_1 is Low or High. Further, the EEO signal from the third AND circuit 33_2 is supplied to the MPU 21_1 through the EEO input terminal 47_1.

  The MPU 21_1 controls data input / output based on the received EEO signal. At this time, the MPU 21_1 may generate an EEO signal corresponding to the control state of the input / output of the data and transmit this to the third AND circuit 33_1.

  That is, each slave device 12 can identify the presence or absence of a lower-level slave device that desires data communication via the received EEO signal, and can open the transmission line according to the identified result. Incidentally, each slave device 21 may be directly connected to the host device 15 via a cable depending on the connection status, may transmit a control signal RTS, or itself transmits a control signal CTS. Therefore, the second AND circuit 32 may be substituted for the role of the third AND circuit 33 described above. Similarly, when each slave device 21 is directly connected to the host device 15, not only the control signal ESO but also the control signal CTS may be transmitted to the first AND circuit 31. Therefore, the first AND circuit 31_n in all the slave devices 21 may be able to obtain a logical product calculated between the control signals ESO and the control signal CTS.

  Note that the communication system 1 to which the present invention is applied is not limited to the above-described embodiment. For example, when the slave device 12_x specified by the host device 15 is specified, the transmission line may be opened so as to realize communication only between the slave device 12_x and the host device 15.

  In this case, when the ID numbers assigned in advance for each slave device 21 are sequentially assigned ID1, ID2,..., IDn from the slave device 12_1 to the slave 12_n, first, the control signal CTS indicating prohibition from the host device 15 is provided. Is output. As a result, all slave devices 21 connected in a daisy chain from the host device 15 are in a state where communication is prohibited.

  Next, an ID number of a desired slave device 12 that desires communication with the host device 15 is designated. In such a case, for example, when the slave device 12_2 is designated, ID2 as the ID number of the slave device 12_2 is included in the control signal CTS (ESO) or transmitted in the RXD. The slave device 12_2 receives the ID number and confirms that it communicates with the host device 15. Then, the MPU 21_2 outputs a control signal EEO indicating prohibition via the EEO output terminal 46_2. By receiving this control signal EEO, the upper slave device above the slave device 12_2 can identify that there is at least one lower slave device that desires data transmission, and prohibits data transfer to the transmission line. can do.

  Thus, after the transmission line is established only between the host device 15 and the slave device 12_2, the slave device 12_2 transmits the data TXD to the host device 15. Similarly, the host device 15 transmits data RXD to the slave device 12_2. After the transmission of the data TXD is completed, the slave device 12_2 transmits the control signal EEO indicating “communication enabled”, thereby transferring the right to use the transmission line to the upper slave device.

  3 and 4 are time charts showing the processing procedure of the communication system 1 to which the present invention is applied. When communication is performed between the host device 15 and the slave device 12_1 based on the RS-232C transmission method, the host device 15 transmits data RXD to the slave device 12_1 and indicates prohibition as illustrated in FIG. A control signal CTS is transmitted to the slave device 12_1. As a result, lower slave devices after the slave device 12_1 can realize data communication between the host device 15 and the slave device 12_1 without interfering with other data as a result of the prohibition of data communication.

  At the next timing, the slave device 12_1 analyzes the data TXD from the host device 15 and transmits a control signal RTS to the host device 15. When the data TXD is returned to the host device 15, the control signal RTS indicating prohibition is continuously sent. On the other hand, when the data TXD is not returned, a control signal RTS indicating “communication permitted” is transmitted.

  Note that the slave device 12_1 continues to send a control signal RTS indicating prohibition to the host device 15 even when the data TXD is voluntarily output. Then, after the output of the data TXD is finished, the control signal CTS indicating “prohibited” is output.

  When link communication is performed between the host device 15 and the slave devices 12_1 and 12_2, as illustrated in FIG. 4, the host device 15 transmits the data RXD to the slave devices 12_1 and 12_2 at the timing t1. At the same time, a control signal CTS indicating prohibition is transmitted to the slave device 12_1. As a result, lower slave devices after the slave device 12_1 can realize data communication between the host device 15 and the slave device 12_1 without interfering with other data as a result of the prohibition of data communication. Further, at the same timing t1, the slave device 12_1 restricts communication in the slave device 12_2 by sending a control signal ESO indicating “prohibited” to the slave device 12_2.

  At the next timing t2, the slave device 12_1 and the slave device 12_2 analyze the data TXD from the host device 15 and transmit a control signal RTS to the host device 15. When the data TXD is returned to the host device 15, the control signal RTS indicating “prohibited” is continuously sent at the timing t3. On the other hand, when the data TXD is not returned, a control signal RTS indicating “communication permitted” is transmitted. Incidentally, at this timing t3, the slave device 12_1 transmits an ESO signal indicating “prohibited” to the lower slave device (slave device 12_2).

  At the next timing t4, the slave device 12_2 continues to send the control signal RTS indicating “prohibited” when returning the data TXD to the host device 15. The slave device 12_2 sets the control signal EEO to “prohibited” at timings t3 and t4, and changes the control signal EEO to “communicable” at the end of returning the data TXD.

  When the slave device 12_1 voluntarily outputs the data TXD, the control signal RTS indicating “prohibited” is transmitted to the host device 15 at the timing t5, and the control signal ESO indicating “prohibited” is transmitted to the slave device 12_1. Transmit to the device 12_2. Further, after the output of the data TXD is completed, the host device 15 outputs a control signal CTS indicating “prohibited” at the timing t6, whereby the slave device 12_2 is prohibited from data communication at the timings t5 and t6. Therefore, it becomes a standby state.

  In the example described above, the case of half-duplex communication has been described as an example. However, the present invention is not limited to such a case, and the same applies to the case of full-duplex communication.

  In the above-described example, the case where the logical product of the control signal from the higher-level slave device or the host device and the control signal generated based on the data transfer status is described. However, the present invention is limited to this case. It is not something. For example, a NAND circuit may be used as an alternative to an AND circuit that calculates a logical product. In such a case, the relationship between Low and High at each signal level is the reverse of this embodiment.

  Note that the communication system 1 to which the present invention is applied is not limited to the case where serial communication is performed, and can of course be applied to a system that performs parallel communication.

It is a block diagram of the communication system to which this invention is applied. It is a block diagram of the electronic device to which this invention is applied. It is a figure which shows the process sequence of the communication system to which this invention is applied. It is a figure which shows the other process sequence in the communication system to which this invention is applied. It is a figure which shows the conventional measurement system. It is a figure which shows the conventional measurement system provided with RS-485 communication function. It is a figure for demonstrating about the conventional measuring system which gave the link function to the unit side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Communication system, 12 Slave apparatus, 13 Measuring unit, 15 Host apparatus, 21 MPU, 22 Transmission control part, 31 1st AND circuit, 32 2nd AND circuit, 33 3rd AND circuit, 34 4th AND circuit

Claims (4)

In a communication system in which at least one slave device is daisy chain connected between the lowest slave device located at the end and the host device ,
The host device transmits a slave control signal to the connected slave device,
The slave device connected between the host device and the lowest slave device is:
Data generated at least in the slave device in response to a slave control signal received via the first control terminal from the host device or the host device connected between the slave device and the host device Control means for transferring the slave control signal to a higher-level slave device or the host device, and generating a first logic signal based on the data transfer status;
First logical product calculating means for calculating a logical product of the slave control signal and the first logical signal generated by the control means;
Transmission means for transmitting a slave control signal, Previous Symbol lower slave device a logical product calculated by the first logic calculating means for the lower slave devices connected to the lower side of the slave device,
A second logic that calculates a logical product of the slave control signal transmitted from the slave slave device connected to the lowest slave device with respect to the slave device and the second logic signal generated by the control means. Product calculating means,
The control means transfers at least data generated in the slave device to the upper slave device or host device in response to a slave control signal received from the lower slave device via the second control terminal, Further, the second logic signal is generated based on the data transfer status, and the first logic signal corresponding to the data transfer status at the end of transfer of the data to the upper slave device or the host device. Produces
The transmission means transmits the logical product calculated by the second logical product calculation means to the upper slave device or host device as a slave control signal for the upper slave device or host device,
In the case of outputting data to the upper slave device or the host device connected between the slave device and the host device, the logical product calculated by the first logical product calculation means is sent to the lower slave device. When the data transfer is completed, the logical product calculated by the first logical product calculation means is transmitted to the lower slave device as a slave control signal indicating that data transfer is prohibited. There is a slave device that transmits data to the slave slave device as a slave control signal indicating that data transfer is permitted to the device, and transmits data when the data transfer is completed. when receiving a slave control signal indicating that, as transfer priority to the output of the data to a lower slave device, and more To the upper level slave device in a position, a communication system, characterized by transferring the data by serial communication in a state in which no priority in the output of the data. Wherein each slave device, and is the host device, a communication system according to claim 1, wherein the forwarding based on the data in the RS-232C transmission scheme. In an electronic device daisy chained between the lowest slave device located at the end and the host device ,
Generated at least in the electronic device in response to a slave control signal received via the first control terminal from the host device or the host device connected between the electronic device and the host device Control means for transferring data to an upper slave device or the host device which is a transmission source of the slave control signal, and generating a first logic signal based on the data transfer status;
First logical product calculating means for calculating a logical product of the slave control signal and the first logical signal generated by the control means;
Transmission means for transmitting a slave control signal, Previous Symbol lower slave device for the lower slave device a logical product calculated is connected to the least significant slave device side of the electronic device by said first logic calculating means,
A second logic for calculating a logical product of a slave control signal transmitted from a lower slave device connected to the lowest slave device with respect to the electronic device and a second logical signal generated by the control means; Product calculating means ,
The control means transfers at least data generated in the electronic device to the upper slave device or host device in response to a slave control signal received from the lower slave device via the second control terminal, Further, the second logic signal is generated based on the data transfer status, and the first logic signal corresponding to the data transfer status at the end of transfer of the data to the upper slave device or the host device. Produces
The transmission means transmits the logical product calculated by the second logical product calculation means to the upper slave device or host device as a slave control signal for the upper slave device or host device,
The control means includes
In the case of outputting data to the upper slave device or the host device connected between the electronic device and the host device, the logical product calculated by the first logical product calculation means is sent to the lower slave device. When the data transfer is completed, the logical product calculated by the first logical product calculation means is transmitted to the lower slave device as a slave control signal indicating that data transfer is prohibited. There is a slave device that transmits data to the slave slave device as a slave control signal indicating that data transfer is permitted to the device, and transmits data when the data transfer is completed. when receiving a slave control signal indicating that, as transfer priority to the output of the data to a lower slave device, a higher For a higher-level slave device, the electronic device, characterized by transferring the data by serial communication in a state in which no priority in the output of the data. 4. The electronic apparatus according to claim 3 , wherein the control unit transfers the data based on an RS-232C transmission method.

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