JP3234240B2 - Control method of serial port of programmable controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a programmable controller capable of communicating with a built-in serial port.

[0002]

2. Description of the Related Art Serial communication required by a programmable controller includes a function of a service unit of a computer link to return a response and a measuring instrument having a programmable controller and another serial port in an arbitrary procedure. There are two types of functions for performing general-purpose communication with a computer.

[0003]

However, since a serial port could not be provided too much due to a cost problem or a size problem, a conventional programmable controller has two of these two functions. Only one of the functions could be satisfied. An object of the present invention is to provide a control method for a serial port of a programmable controller which can support both functions of computer link and general-purpose communication by switching communication control processing of the serial port.

[0004]

According to the present invention, in order to achieve the above-mentioned object, a programmable controller includes one or more serial ports for serial communication,
A parameter area for writing a parameter for selectively using the serial port is provided, and a parameter for selecting and setting one of a general-purpose communication function based on a command for performing serial communication and a computer link function by a dedicated procedure is set in the parameter area, The communication control function of the serial port is switched based on the above parameters.

[0005]

According to the present invention, a parameter for selecting one of the general-purpose communication and computer link functions is written in the parameter area, and the parameter in this parameter area is checked at the time of transmission / reception processing. Port communication control processing can be switched,
Therefore, it can be used for both general communication and computer link.

[0006]

FIG. 1 shows a circuit configuration of a programmable controller used in the present invention. This programmable controller includes a CPU 1 for performing overall signal processing, a ROM 2 for storing computer link and other dedicated procedures such as system programs, and a user. A RAM 3, which stores a program, sets a work area and a parameter area to be described later, and configures a reception buffer and a transmission data storage area during communication, a serial port 4, and an I / O interface 5 It is provided.

[0007] The parameter area set in the RAM 3 is, for example, an address 0 is an area for setting a function selection flag, an address 1 is an area for storing a head address of a reception buffer when a general communication function is selected, and an address 2 is an area for storing a head address. When selecting the general-purpose communication function, it is used to specify the capacity of the reception buffer. The function selection flag is, for example, “0”
When "1" is set, the computer link function is selected, and when "1" is set, the general-purpose communication function is selected and set.

According to the method of the present invention, the above-described parameters are used.
When a function selection flag is set in the data area, the CPU 1 sets the serial port 4 based on the set flag.
Of the communication control process of (1). FIGS. 2 and 3 show the flow of the transmission / reception processing.
As shown in (2), the CPU 1 checks the parameter area, and if the set function selection flag is “1”, sets the control processing for general-purpose communication and sets the serial port 4
If no "CR" code is received, increment the number of received bytes, read the reception buffer point, and set data in the reception buffer. This receiving process is repeatedly performed until the “CR” code is received.

The transmission in this general-purpose communication is performed by a transmission command. For example, in the ladder diagram of FIG. 4, when the execution condition a is turned on, the transmission command is composed of a code F of the application command and No. [m] of the application command. Based on the sending instruction,
The start address S of the transmission buffer for which transmission is requested and the number of transmission bytes stored at the start are copied to the general-purpose communication processing work areas A and B shown in FIG.

Here, the transmission buffer has an area configuration as shown in FIG. 5, and the number of transmission bytes is stored at the head address 0, and transmission data is stored at subsequent addresses 1 to N + 1. Then, the transmission interrupt is permitted, the function selection flag in the parameter area is checked, and if the general-purpose communication function is set, the CPU 1 switches to the general-purpose communication control processing, and first stores it in the general-purpose communication processing work area A. Capture the number of transmitted bytes.

If the number of transmission bytes is not 0, after subtracting 1 from the number of transmission bytes, the pointer of the start address of the transmission buffer stored in the general-purpose communication processing work area B is obtained. The data is read and transmitted to the serial port 4. After this transmission, the pointer of the start address of the transmission buffer stored in the work area B is incremented. Such processing is repeated until the number of transmission bytes becomes 0, and when the number of transmission bytes becomes 0, the general-purpose communication is terminated.

The above-mentioned transmission / reception is the case of general-purpose communication. However, when the function selection flag is set to "0" and the function of the computer link is selected, the following processing is performed. First, in the case of the reception processing, the same processing as in the case of the general-purpose communication is performed, but in the case of the computer link, the RAM 3 has dedicated transmission / reception buffers E and F shown in FIG. When the CPU 1 determines that the computer link function has been selected, the CPU 1 starts the receiving process based on the dedicated procedure of the computer link service unit.

On the other hand, in the case of transmission processing, when the CPU 1 determines that the computer link function is selected, the number of transmission bytes of the dedicated transmission buffer E and the head of the dedicated transmission buffer are determined according to a dedicated procedure based on the computer link service unit. After copying the addresses to the work areas C and D, the same processing as the above-described general communication processing is performed.

[0014]

According to the present invention, a programmable controller is provided with one or more serial ports for serial communication, a parameter area for writing a parameter for selectively using the serial port, and an instruction for performing serial communication is provided in the parameter area. A parameter for selecting and setting one of the general-purpose communication function based on the computer link function and the computer link function based on the special procedure is set, and the communication control function of the serial port is switched based on the above parameters. By writing a parameter to select one of the above, by checking the parameter in this parameter area at the time of transmission / reception processing, it is possible to switch the communication control processing of the serial port.
It can be properly used for a computer link, and as a result, there is an effect that cost increase and size increase of the programmable controller can be avoided.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart of a receiving process according to one embodiment of the present invention.

FIG. 3 is a flowchart of a transmission process according to an embodiment of the present invention.

FIG. 4 is a ladder diagram for explaining a general-purpose communication instruction.

FIG. 5 is an explanatory diagram of a work area for general-purpose communication.

FIG. 6 is an explanatory diagram of a work area of a computer link.

[Explanation of symbols]

 1 CPU 2 ROM 3 RAM 4 serial port 5 I / O interface

Claims (1)

(57) [Claims] A programmable controller includes one or more serial ports for serial communication, a parameter area for writing parameters for selectively using the serial ports, and general-purpose communication based on a command for performing serial communication in the parameter area. A control method for a serial port of a programmable controller, wherein a parameter for selecting and setting one of a function and a computer link function by a dedicated procedure is set, and a communication control function of the serial port is switched based on the parameter.