JPH09326700A - Multi-channel d/a converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify circuit constitution and to perform a high-speed processing. SOLUTION: This D/A converter is composed of D/A conversion parts 11 -1n to which digital amount inputs D1-Dn are successively updated by an arithmetic cycle and inputted and a signal selection circuit 2 for successively outputting digital amount selection inputs DS1-DSn successively turned ON by the arithmetic cycle respectively to the conversion parts 11 -1n as channel selection signals and data write signals. Since a channel is selected and the timing of successive data write to the conversion parts 11 -1n is managed in the signal selection circuit 2, the need of a conventionally required external timing circuit is eliminated, the timings of channel selection and write are matched and thus, troubles by the timing are not generated and the arithmetic cycle is changed from conventional 60ms to be equal to or less than 20ms.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-channel D / A converter for converting digital quantities of several points in measurement and control signals into analog quantities.

[0002]

2. Description of the Related Art In programmable controllers (PC), there is a multi-channel D / A conversion unit that converts a digital quantity in the PC into several analog quantities and outputs the analog quantity.
This conversion unit includes a plurality of D / A conversion units 1 as shown in FIG.
₁ to 1 _n are provided, and the digital amounts of the data addresses ₁ to _n in the PC are converted into analog amounts by the D / A converters 1 ₁ to 1 _n , and the analog outputs A1 to An are output. There is.

[0003]

[Problems to be Solved by the Invention] Conventional multi-channel D-
As shown in FIG. 4, the data conversion method of the A conversion device (unit) is such that the data is updated at a calculation cycle T _S (= 60 ms) and each D / A conversion unit (chip) 1 ₁ to 1 _n (FIG. 3). type in the channel switching circuit, external timing processing circuit (not shown) by the timing shown a chip select signal CS1~CSn and the write signal WR D / a converter section 1 ₁
To 1 _n to switch channels and write data, and the updated data D1 to Dn are sequentially converted by the D / A converters 1 ₁ to 1 _n of the selected channels to output analog outputs A1 to However, the timing processing circuit is complicated, which is an obstacle to speeding up, downsizing, and cost reduction.

The present invention has been made in view of the above-mentioned problems of the prior art, and the purpose thereof is to provide each D
A multi-channel A- that simplifies the timing function for writing digital values to the A / A converter and enables high speed and downsizing.
It is to provide a D conversion device.

[0005]

Multichannel D of the present invention
The -A converter includes a plurality of D-A conversion units that receive digital amount inputs updated in the calculation cycle and a plurality of digital-amount selection inputs that sequentially turn on in the calculation period to the plurality of D-A conversion units. A signal selection circuit that sequentially outputs as a channel selection signal and a data write signal is provided, and the signal selection circuit manages the timing of writing data to each DA converter.

[0006]

1 shows a circuit configuration of a multi-channel D / A conversion device, and FIG. 2 shows a D / A conversion time chart. In FIG. 1, 1 ₁ to 1 _n are D / A converters, 2 is each D of digital amount selection inputs DS1 to DSn by internal processing
A / A converters 1 ₁ to 1 _n are signal selection circuits, 3 is D / A
A reference voltage circuit for giving an analog reference voltage to the converters 1 ₁ to 1 _n , S _{1 to} S _n are D / A converters 1 by switching the reference voltage from the circuit 3 and the external analog signals A _EX 1 to A _EX n. ₁ to 1 _n
It is a switch to input to, and is always on the reference voltage side.

Digital quantities D1 to Dn updated at the operation cycle T _S as shown in FIG. 2A are input to the input terminals of the D / A converters 1 ₁ to 1 _n . The signal selection circuit 2 is shown in FIG.
As shown in (b), the digital amount selection inputs DS1 to DSn which are sequentially turned on in the cycle T _S are input, and the signals sequentially selected by the circuit are sequentially selected as the chip select signal CS and the write signal WR in the D / A conversion unit 1 ₁ Type in ~ 1 _n .

Therefore, the D / A converters 1 ₁ to 1 _n are connected to the digital quantity selection input DS sequentially output from the signal selection circuit 2.
Channels are sequentially selected by 1 to DSn, data is written, and the selected and written D /
Input digital quantities D1 to Dn by the A converters 1 ₁ to 1 _n
Is D / A converted to analog output A as shown in FIG. 2 (c).
1 to An are sequentially output.

If the switches S _{1 to} S _n are switched to the external analog signals A _EX 1 to A _EX n side, the D / A converter ₁₁
It _{means that} the standard value of ~ 1 n is multiplied by A _EX 1 ~ A _EX n,
Digital quantity inputs D1 to Dn from D / A converters 1 ₁ to 1 _n
Analog output A1~An is obtained by multiplying the external analog signal A _EX 1 to A _EX n and.

According to this D / A converter, a timing processing circuit is not required, and there is no fear of occurrence of a trouble due to timing. Therefore, it is possible to perform high-speed processing with the operation cycle T _S set to 20 ms or less from the conventional 60 ms. became.

[0011]

Since the present invention is configured as described above, it has the following effects.

(1) Only by updating the digital quantity input and the digital quantity selection input in synchronization, the D /
A conversion is possible.

(2) Since an external timing processing circuit for complicated writing is not required and there is no fear of occurrence of trouble due to timing, a unit which is easy to use as a multi-channel A / D conversion unit can be obtained.

(3) Therefore, high speed processing, downsizing and cost reduction can be achieved.

(4) By inputting an external analog signal, it can be used as a D / A conversion multiplication calculator.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an A / D conversion device according to the present invention.

FIG. 2 is a time chart of D / A conversion.

FIG. 3 is an explanatory diagram of a D / A conversion method of a conventional PC D / A conversion unit.

FIG. 4 is a time chart of conventional D / A conversion.

[Explanation of symbols]

1 ₁ to 1 _n ... D / A converter 2 ... Signal selection circuit 3 ... Reference voltage circuit T _S ... Calculation cycle

Claims (2)

[Claims] 1. A plurality of D-A converters for inputting digital quantity inputs updated in a calculation cycle, and a plurality of digital quantity selection inputs sequentially turned on in a calculation cycle are channeled to the plurality of DA converters, respectively. A multi-channel D-, characterized in that it has a selection signal and a signal selection circuit for sequentially outputting as a data writing signal, and the signal selection circuit manages the timing of data writing to each DA converter. A converter. 2. A switching means for switching and inputting a reference voltage and an external analog signal to each DA conversion section according to claim 1, so that an analog signal of a product of a digital amount and an external analog signal can be output. A multi-channel D / A conversion device characterized in that