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Attachment Logic for Direct Entry Units

IP.com Disclosure Number: IPCOM000086608D
Original Publication Date: 1976-Oct-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

O'Neal, DM: AUTHOR

Abstract

This direct-attachment logic unit provides the control logic to interface up to 12 IBM Data Entry Units (DEUs) directly to an IBM System/7 5013 Digital I/O Module. The attachment provides polling techniques via circuit sharing with relays, selection of DEUs, and has reduced noise sensitivity. The IBM 2796 DEU is an operator-oriented device for use in a factory. It contains a badge-card reader, data switches and various control switches. The IBM 2797 DEU is like the 2796 DEU, but has a 10-key numeric keyboard and a six-position visual display for checking data. The DEUs send their numeric data as two distinct polarity sensitive resistance values under control of the attachment. Both the 2796 and 2797 DEUs transmit nineteen numeric characters plus an end of transmission (ETX) character.

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Attachment Logic for Direct Entry Units

This direct-attachment logic unit provides the control logic to interface up to 12 IBM Data Entry Units (DEUs) directly to an IBM System/7 5013 Digital I/O Module. The attachment provides polling techniques via circuit sharing with relays, selection of DEUs, and has reduced noise sensitivity. The IBM 2796 DEU is an operator-oriented device for use in a factory. It contains a badge-card reader, data switches and various control switches. The IBM 2797 DEU is like the 2796 DEU, but has a 10-key numeric keyboard and a six-position visual display for checking data. The DEUs send their numeric data as two distinct polarity sensitive resistance values under control of the attachment. Both the 2796 and 2797 DEUs transmit nineteen numeric characters plus an end of transmission (ETX) character. After a Request is initiated by the DEU operator, the 19 data characters are received by energizing the start magnet in the DEU.

This attachment allows the IBM System/7 program to perform three basic functions: select a DEU and read its resistance, reverse the polarity of the current through the DEU, and energize the DEU magnet.

Using combinations of these functions in the proper sequence, the following operations are accomplished: 1. Detect if DEU is attached and ready.

2. Detect if DEU is requesting service.

3. Initiate DEU data scan.

4. Read DEU data.

5. Transmit good/bad answer to DEU.

Select and Read. The figure illustrates the attachment with DEUs attached. The resistance presented by the DEU's is read by energizing the proper select relay 1-n (write digital output (DO) bit 2/10 through 7/15) and reading digital input (DI). The bit assignments are wired by the customer, but Dl bits 0-2 are typical.

With a select relay energized, current flows from the power (PWR) terminal through polarity relay 3 and select relay contacts on line 1 to the selected DEU. The return is on line 2 through the same two relays and through detection circuit 4 to ground. Detection circuit 4 converts this current value to 1 of 4 bit patterns, as shown in the chart. The HEX value assumes 4 bits. These data lines are wired by the customer to contact sense DI where they are read with a read...