Browse Prior Art Database

Software Simulation of Paper Tape Output

IP.com Disclosure Number: IPCOM000076813D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 56K

Publishing Venue

IBM

Related People

Ellsworth, GM: AUTHOR [+3]

Abstract

Paper tape readers employed to operate machine tools supply output data, a character at a time. Characters are grouped within blocks of data. Characters are requested by block. Each output character so supplied is accompanied by a short duration "sprocket pulse" which causes the receiving device to accept the character.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Software Simulation of Paper Tape Output

Paper tape readers employed to operate machine tools supply output data, a character at a time. Characters are grouped within blocks of data. Characters are requested by block. Each output character so supplied is accompanied by a short duration "sprocket pulse" which causes the receiving device to accept the character.

The above software system supplies computer output directly to machine tools by simulating the paper tape output.

The sequence is initiated by an interrupt 10 from a hardware timer in the computer. In step 11, any accessed software timer in use ("busy") is incremented by one. Step 12 checks whether the increment caused an arithmetic status change of the accessed timer. This allows different timers to be used to establish, by differing counts per status change, different data rates. If the status has not changed, the next timer is accessed and steps 11 and 12 are repeated. If the status has changed, step 12 branches to the next phase indicated by the timer.

Phase 1 begins with step 13, which designates as "active" all devices serviced by the timer that continued to demand data since they were last supplied data. Step 14 supplies the next character of data through an output register to each device demanding data.

Step 15 then checks whether all timers have been serviced. If so, exit step 16 is taken to wait for the next hardware interrupt at step 10. If not all the timers have been serviced for this interrupt, the method returns to step 11 to increment the next accessed "busy" timer.

Phase 2 begins with step 17, which updates the strobe byte to include the active devices designated in phase 1 for that timer. The strobe byte has a binary bit position for each device associated with the timer. Step 17 sets a binary "1" in each bit position corresponding to an "active" device and leaves the other bits "0". Step 17 then supplies the strobe byte at the strobe output. Thus, a short duration pulse is transmitted on each strobe output line corresponding to a 1 bit. The device responds by reading the data character supplied at an output therefor in step 14. Step 18 then accesses the n...