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Browse Prior Art Database

Analog To Digital Converter

IP.com Disclosure Number: IPCOM000094561D
Original Publication Date: 1965-Mar-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 4 page(s) / 46K

Publishing Venue

IBM

Related People

Walton, CA: AUTHOR [+3]

Abstract

The application of digital computer to process control problems usually requires an analog-to-digital converter for the purpose of converting analog process data into machine usable form. In this system, the analog-to-digital conversion is accomplished by hardware which is an integral part of the computer instead of the usual outboard form.

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Analog To Digital Converter

The application of digital computer to process control problems usually requires an analog-to-digital converter for the purpose of converting analog process data into machine usable form. In this system, the analog-to-digital conversion is accomplished by hardware which is an integral part of the computer instead of the usual outboard form.

Digital computers commonly contain a core storage 1. This has locations in which information is stored and withdrawn under the control of memory address register (MAR) 2 and core drivers 3 and 4. Increment-decrement unit 5 allows the number contained in MAR 2 to be modified and regenerated. Data is read from the selected address into memory buffer register (MBR) 6 and memory output bus 7.

The contents of MBR 6 on bus 7 can be gated into arithmetic unit 8 and either added or subtracted to the value in accumulator register 9. Similarly, the contents of MBR 6 can be transferred over bus 7 to address drivers 10 and 11 for input-output multiplexer 12. This connects the computer through lines 13 to the process. All foregoing elements are contained or available in digital computers for process control.

To provide for conversion of analog data to digital form, a resistance ladder network and associated switches 14 can be controlled by register 9. The network 14 output is an analog voltage representing the digital value in register 9. Such output is applied to one input of comparator 15. The process signal selected by multiplexer 12 is applied to the other input of comparator 15 whose output signal on line 16 has one of two values. A high, or add, signal indicates the process signal to be greater than the network 14 output. A low, or subtract, signal indicates the process signal to be smaller than the network 14 output. The control circuits of the computer include add-subtract indicator 17 set from the comparator 15 output or other circuits under program control. The control circuits provide for testing indicator 17. This is so that program branches can be made dependent on the status of indicator 17 at a given point in a sequence of computer instructions. A value in register 9 can be gated onto memory input bus
18.

Conversion to digital form of an analog process signal selected by multiplexer 12 involves the following sequence of program steps or instructions. Since the actual instruction is dependent on the particular computer to be used, the instructions are described in functional terms.

Drivers 10 and 11 are set to the desired address by reading from a predetermined location in storage 1 and gating the data contained in it to the address drivers. This results in application of the process signal at the selected multiplexer point to one input of comparator 15. MAR 2 is set to the storage location which contains data indicating the value for the first comparison step.

The data at this address is read from storage through unit 8 where it is added to the value, now zero, in...