JPH0814783B2 - Analog input / output device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog input / output device for processing various analog signals obtained from a field by a computer and outputting the analog signals to the field again. Relates to an analog input / output device for connecting a sensor or an actuator to a computer that handles digital signals.

(Prior Art) FIG. 4 is a configuration block diagram showing an example of a system using a conventional analog input / output device. In the figure, CP
Is a computer that handles digital signals, ANI is an analog input device that converts the analog signal from the field into a standardized signal that can be processed by computer CP, and outputs it.ANO is an analog output that outputs the signal from computer CP to the field. It is a device.

In the analog input device ANI, MXI is an input multiplexer, which sequentially selects a large number of input analogs Vn1 to Vnn and applies them to the buffer amplifier BA, and AD is an A / D converter that converts an analog signal into a digital signal, IF1 is an interface that outputs the output of the A / D converter AD to the computer CP side via the bus BS.

In the analog output device ANO, IF2 is an interface that receives data from the computer CP, DA is a D / A converter that converts a digital signal into an analog signal, and MX2 is a D / A converter D.
The analog signal from A is connected to each sample and hold circuit SH1 to SH
It is an output multiplexer that sequentially supplies to n.

(Problems to be Solved by the Invention) In the conventional system configured as described above, since the input side and the output side have different functions, the analog signal input / output device is different from that for the input side. 2 for output side
It was necessary to prepare different types of devices. For this reason, there are problems that the number of devices increases and the configuration becomes complicated.

The present invention has been made in view of the above problems, and an object thereof is to provide an analog input capable of providing functions of an input side and an output side by one type of device having a simple structure. To provide an output device.

(Means for Solving the Problem) FIG. 1 is a block diagram showing the basic configuration of the present invention. In the figure, MX1 indicates a large number of analog signals AV1 to AVn.
Input multiplexer for selecting and inputting AD, AD is A / D conversion means for converting the analog signal selected by this input multiplexer MX1 to a digital signal, DA is D / A conversion means for converting a digital signal to an analog signal, MX2 Is this D / A
An output multiplexer for selecting and outputting the analog signal from the converting means DA to a large number of analog signal holding means SH1 to SHn, FB is a feedback means for giving the signal from the output multiplexer MX2 to the input side of the input multiplexer MX1, M
P is a microprocessor that controls the input multiplexer MX1, the A / D conversion means AD, the D / A conversion means DA, and the output multiplexer MX2.

Note that MU is a memory that stores a database, and CP
Is a high-order computer connected via a high-order bus BS.

(Operation) The microprocessor MP has a D / A conversion means D when the power is turned on.
While outputting a predetermined signal from A to the output multiplexer MX2, the signal from the feedback means FB is read through the input multiplexer MX1, and the value of the read signal causes the device to function as an analog input device or as an analog output device. Decide if you want it to work.

(Example) Hereinafter, the example of the present invention is described in detail using drawings.

FIG. 2 is a configuration block diagram showing an embodiment of the present invention. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals. The A / D conversion means AD includes a comparator CMP having a signal from the input multiplexer MX1 as one input, a register RG in which data is stored according to the signal from the comparator, a microprocessor MP, and D / D. A converter DA and D / A
The switch SW applies a signal from the converter to the other input terminal of the comparator CMP. Microprocessor mp
Is connected to the upper computer CP via the upper interface IF.

Here, when the device is used as an analog input device, the signal holding means SH1 to SHn as shown in the figure are not required on the output side of the output multiplexer MX2 and are not mounted in the device.

That is, the device targeted by the present invention is assumed to be applied to, for example, a process control device, and its input side is a device (input device) that functions as an analog input device for receiving a measurement signal from a process. Card)
On the output side, a device (output card) that functions as an analog output device for outputting an analog signal for driving an operating end such as a valve is provided.

In the present invention, when a plurality of devices of one type are prepared and this device is used as an analog input device,
When the signal holding means (SH1 to SHn) is not connected and used as an analog output device, the signal holding means (SH1
~ SHn) is connected.

Then, when the power is turned on, it is automatically determined whether the device itself functions as an analog input device or an analog output device from the value read by the device itself through the feedback means, and the subsequent operation is performed. The configuration is based on a decision.

 The operation of the device configured as described above will be described below.

FIG. 3 is a flowchart showing an example of the operation performed by the microprocessor MP when the power is turned on.

When the device is powered on, the microprocessor MP
First, connect the switch SW to the contact d side,
In the output multiplexer MX2, the channel CH21 is connected and the D / A conversion means DA outputs a predetermined voltage, for example, a voltage of 1V (steps 1 and 2).

Next, the switch SW is connected to the contact a side, the channel CH1n of the input multiplexer MX1 is connected, and the signal of this channel CH1n is read (steps 3 and 4). In this state, the circuit composed of the comparator CMP, the register RG, the microprocessor MP, and the D / A conversion means DA forms an A / D conversion loop via the switch SW and is applied to one end of the comparator CMP. Signal is converted to a digital signal.

Next, it is determined whether the magnitude of the A / D converted signal is the predetermined voltage output in step 2 (step 5).

Here, if the signal holding circuits SH1 to SHn are connected to the output side of the output multiplexer MX2, the signal held here is applied to the input side of the input multiplexer MX1 via the feedback means FB. . On the other hand, the signal holding circuit SH1 is connected to the output side of the output multiplexer MX2.
Assuming that ~ SHn are not connected, the signal applied to the input side of the input multiplexer MX1 via the feedback means FB is around 0V.

If the magnitude of the read signal is a predetermined voltage, for example, 1 V in step 5, a program for operation is set so as to operate as an analog input device (step 6).

On the other hand, if the voltage is not the predetermined voltage in step 5,
For example, when the voltage is near 0 V, the operation program is set so as to operate as an analog input device (step 7).

When the power is turned on, the microprocessor MP first performs such an operation to determine whether or not the signal holding unit is connected, and accordingly operates as an analog input device or an analog output device thereafter. Have decided.

In step 6 which operates as an analog output device, the switch SW is connected to the contact point d side and, for example, the data base sent to the memory MU from the host computer CP and stored therein is read at a predetermined cycle, and this is read by D / A is converted and output to the signal holding means SH1 to SH2 for each point via the output multiplexer MX2.

In step 7 which operates as an analog input device, the switch SW is connected to the contact a side, and the input multiplexer MX
Via 1, the input signals AV1 to AVn at each point are sequentially D / A converted,
Stored in the memory MU as a standardized database.

The database stored here is read by the higher-level computer CP as needed.

In the above embodiment, the A / D conversion means is a comparator CMP,
The loop is composed of a register RG, a microprocessor MP, a D / A converter DA, and a switch SW, but the switch SW may be omitted or the register SW may be omitted.
The RG may be one inside the microprocessor MP. Further, an A / D converter may be provided on the input side of the microprocessor.

(Effects of the Invention) As described in detail above, according to the present invention, the main configuration of the analog input device and the analog output device can be made common. An analog input / output device having a function with the output side can be realized, and the cost can be reduced.

That is, in the present invention, a plurality of devices of one type are prepared, and when this device is used as an analog input device, the signal holding means (SH1 to SHn) is not connected to the output side, and the device is used as an analog output device. When used, it is configured to connect (implement) signal holding means (SH1 to SHn) to the output side, and when the power is turned on, the device itself automatically converts the analog value from the value read via the feedback means. It is configured such that it is determined whether to function as an input device or an analog output device, and subsequent operations can be performed based on the determination.

Therefore, by preparing only one type of device, it is possible to deal with both the analog input device and the analog output device, which has the effect of reducing the cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic configuration of the present invention, and FIG.
FIG. 3 is a configuration block diagram showing an embodiment of the present invention, FIG. 3 is a flow chart showing an example of operation performed by a microprocessor, and FIG. 4 is a configuration block diagram of a conventional device. MX1 …… Input multiplexer MX2 …… Output multiplexer AD …… A / D conversion means MP …… Microprocessor DA …… D / A converter FB …… Feedback means

Claims (1)

[Claims] 1. An input multiplexer for selecting and inputting a large number of analog signals, an A / D conversion means for converting the analog signals selected by the input multiplexer into a digital signal, and a D for converting a digital signal into an analog signal. / A conversion means, an output multiplexer for selecting and outputting an analog signal from the D / A conversion means to a large number of analog signal holding means, the input multiplexer, A / D conversion means, D / A conversion means,
A microprocessor for controlling the output multiplexer, and a feedback means for giving a signal from the output multiplexer to the input side of the input multiplexer, the microprocessor outputs a predetermined signal from the D / A conversion means when the power is turned on. Outputting the signal to the multiplexer and reading the signal from the feedback means through the input multiplexer, and determining whether the device functions as an analog input device or an analog output device according to the value of the read signal. An analog input / output device characterized by.