JP2010003038A - Method of automatically assigning id to each unit in serial connection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically set an ID of an extension unit of each stage only by serially connecting the extension unit. <P>SOLUTION: The extension unit of each stage transmits a signal from a preceding extension unit to a subsequent extension unit while inverting the level of the signal and latches the signal at an transmission initial time. The extension unit of each stage performs ID assignment in a connecting position within the serial connection of the extension unit of each stage based on the level inversion state of the signal input thereto and the delay state from the latch timing, whereby the extension unit of each stage can be serially connected to a PLC without requiring a user to set the ID. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a system for automatically assigning IDs of units at each stage in a serial connection in a system in which units such as expansion I / O are serially connected to a plurality of stages.

A programmable controller (hereinafter referred to as PLC) executes a sequence program and controls a control device connected thereto. Such a PLC includes various units added at the time of system expansion to various units connected at the time of system installation. This expanded unit is hereinafter referred to as an expansion unit in this specification. For example, the input / output unit is referred to as expansion I / O. Such extended I / Os are serially connected to the PLC each time they are added. The extended I / O transmits data from an input device such as a sensor to the PLC in response to a data transmission request from the PLC, or controls an output device such as an actuator in response to a control command from the PLC. For transmission and reception with such a PLC, it is necessary to identify the extended I / O at each stage, and conventionally, an ID is set by a DIP switch (see Patent Document 1). However, such ID setting by the dip switch is troublesome for the user, and even if the ID setting is made by the dip switch, the connection order may be mistaken at the stage of serial connection to the PLC. There are challenges.
JP 2001-024673 A

  An object of the present invention is to enable automatic assignment of IDs to units at each stage within a serial connection as long as a unit such as an expansion I / O is serially connected to the PLC.

  The present invention is a method of automatically assigning an ID to each stage unit when serially connecting a unit to a PLC in a plurality of stages. The PLC transmits a signal of a predetermined level to the first stage unit and transmits the signal. The transmission timing of this signal is latched in each stage unit in synchronization with each other, and each stage unit changes the level of the input signal and transmits it to the next stage unit. Based on the level of the input signal and the transmission timing, an ID indicating its own connection position in the serial connection is automatically assigned.

  Preferably, the change in the level of the input signal is a change in which the level is inverted.

  According to the present invention, each ID can be automatically assigned based on the level of the identification signal and the latch timing by simply serially connecting each of a plurality of expansion units to the PLC. There is no need to set and assign IDs to expansion units at each stage with DIP switches. In addition to making the expansion of expansion units in the PLC system extremely efficient, connecting expansion units with the required IDs to the PLC There is no possibility that an extension unit with another ID is erroneously connected to the position.

  Hereinafter, with reference to the accompanying drawings, an automatic ID assignment method for expansion units in a serial connection according to an embodiment of the present invention will be described. In the embodiment, the expansion unit is described with reference to the expansion I / O. However, the expansion unit is not limited to the expansion I / O and includes other units. FIG. 1 shows a PLC system in which a plurality of stages of expansion I / Os are connected to a PLC, and in the embodiment, four stages of expansion I / Os are serially connected. FIG. 2A shows expansion I / O identification in a serial connection. The signal to be used (identification signal), (b) shows the latch timing of the identification signal, and (c) shows the level inversion state of the identification signal. Referring to these figures, the PLC 10 has a plurality of stages, in the embodiment, four stages, and the expansion I / O 20-23 is serially connected by the bus 30-33 and the identification signal line 40-43. Yes. A latch signal is input from the PLC 10 to each stage expansion I / O 20-23 via a latch signal line 50. The expansion I / O 20-23 at each stage stores the latch timing of the latch signal.

  An input device and an output device (not shown) are connected to the expansion I / O 20-23 at each stage. Control command transmission from the PLC 10 to the expansion I / O 20-23 of each stage and data transmission from the expansion I / O 20-23 of each stage to the PLC 10 are performed via the bus 30-33.

  The identification signal 0 from the PLC 10 is only for the first expansion I / O 20. The identification signal 1-3 for the subsequent stage expansion I / O 21-23 is given from the previous stage expansion I / O 20-22.

  Hereinafter, the identification within the serial connection of the expansion I / O 20-23 of each stage will be described with reference to FIGS.

  The PLC 10 transmits the high-level identification signal 0 shown in FIG. 2A to the first-stage expansion I / O 20 through the identification signal line 40 at the time of control command transmission or data transmission request, etc., while being sent to the latch signal line 50. The latch signal is transmitted at timing t0 synchronized with the transmission. This control command or data transmission request includes the ID of the destination expansion I / O 20-23. The expansion I / O 20-23 in each stage latches the latch signal from the PLC 10 at the timing t0 in FIG. 2B, and calculates the delay time from the latch time using the timing t0 as the latch time.

  The extension I / O 20 is connected to the PLC 10 in the first stage connection position within the serial connection. If the level of the identification signal 0 when received at the timing t0 is high at the first stage connection position, the time Since the reception is performed without a delay time at t0, the extended I / O 20 at the connection position can be identified as the first-stage ID. As a result, by simply connecting the expansion I / O 20 to the connection position of the first stage to the PLC 10, an ID as the first expansion I / O can be automatically assigned to the expansion I / O 20.

  Next, the expansion I / O 20 inverts the level of the identification signal 0 from the high level to the low level as shown in FIG. 2A and outputs the inverted signal to the signal line 41 as the identification signal 1. . The expansion I / O 21 in the next stage is that the signal 1 for identification is at the low level and the time elapsed until the signal is inverted from the high level to the low level, that is, from the timing t0 shown in FIG. Based on the delay time Δt, the expansion I / O 20 at the second connection position in the serial connection from the PLC 10 can be identified as the second expansion I / O 21. As a result, simply by connecting the expansion I / O 21 to the connection position of the second stage to the PLC 10, an ID as the expansion I / O of the second stage can be automatically assigned to the expansion I / O 21.

  Next, the extension I / O 21 inverts the level of the signal 1 from the low level to the high level as shown in FIG. 2A, and outputs the inverted signal to the signal line 42 as the identification signal 2. The expansion I / O 22 in the next stage is based on the fact that the identification signal 2 is at a high level and that the delay time difference from the first latch timing t0 is 2Δt at the time when the identification signal 2 changes to the high level. The expansion I / O 22 at the third connection position in the serial connection from the PLC 10 can be identified as the third expansion I / O 22. As a result, simply by connecting the expansion I / O 22 to the connection position of the third stage to the PLC 10, an ID as the expansion I / O of the third stage can be automatically assigned to the expansion I / O 22.

  Finally, the expansion I / O 22 inverts the level of the signal 2 from the high level to the low level, and outputs the inverted signal to the signal line 43 as the identification signal 3. The expansion I / O 23 at the final stage is based on the fact that the identification signal 3 is at the low level and the delay time difference from the first latch timing t0 is 3Δt at the time when the identification signal 3 changes to the low level. From the serial connection, the expansion I / O 23 at the fourth connection position can be identified as the final expansion I / O 23. As a result, simply by connecting the extension I / O 23 to the PLC 10 at the last connection position, an ID as the last-stage extension I / O can be automatically assigned to the extension I / O 23.

  Each extension I / O 20-23 can identify itself as an ID indicating the number of extension I / Os from the PLC 10 within the serial connection as described above. If the ID of the extended I / O of the command destination or the data transmission request destination is checked to match the ID itself, a response process is performed for the control command or transmission request.

  As described above, in this embodiment, the user automatically assigns an ID to each expansion I / O 20-23 automatically by simply serially connecting each expansion I / O 20-23 to the PLC 10. In addition to making the expansion unit expansion work in the PLC system extremely efficient, the expansion unit with another ID is erroneously connected to the connection position of the expansion unit having the required ID for the PLC. There will be no such thing.

FIG. 1 is a diagram showing a block configuration of a PLC system that identifies extended I / O by an extended I / O identification method according to an embodiment of the present invention. 2A shows a signal (identification signal) used for extension I / O identification within a serial connection, FIG. 2B shows a latch timing of the identification signal, and FIG. 2C shows a level inversion state of the identification signal. FIG.

Explanation of symbols

10 PLC
20-23 Extended I / O
30-33 bus 40-43 signal line 50 latch signal

Claims (2)

  This is a system that automatically assigns IDs to units in each stage when serially connecting units to the PLC in multiple stages. The PLC sends a signal of a predetermined level to the first stage unit and synchronizes with this transmission. Each stage unit latches the transmission timing of this signal, and each stage unit changes the level of the input signal and transmits it to the next stage unit, whereby the signal input to each stage unit. An automatic ID assignment method for an expansion unit, wherein an ID indicating its own connection position within the serial connection is automatically assigned based on the level of the transmission and the transmission timing.   The method according to claim 1, wherein the level change of the input signal is a level inversion.

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