Description
The programme examines the ways in which a ROM may be used for static code conversion, sequencing, repeating states to provide irregular sequences and for storing a duration code.
Metadata describing this Open University video programme
Module code and title: T283, Introductory electronics
Item code: T283; 07
First transmission date: 30-07-1980
Published: 1980
Rights Statement:
Restrictions on use:
Duration: 00:22:41
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Producer: Ted Smith
Contributors: D.(David) Gorham; Mike Meade; Alan Reddish
Publisher: BBC Open University
Keyword(s): Calculators; Digital systems; Traffic lights
Footage description: Brief shot of a logic analyser display. Alan Reddish, holding a pocket calculator as an example of digital electronics, introduces the programme. David Gorham manipulates a seven segment display so that each of the denary digits comes up in turn. He inputs a 7-bit binary word to activate each digit. Gorman goes on to explain that by using a ROM programmed with a particular truth table, the input code can be considerably simplified. Gorham holds up a ROM, an example of a combinational logic device. He connects it to his 7 segment display and is now able to activate each denary digit by inputting a simplified binary code. To illustrate a practical application of this ROM, Gorham adds a counter to the circuit. The denary numbers are now automatically displayed in their correct order. Another application, that of displaying an alphabetical sequence, is then demonstrated. Mike Meade, with an electronic model of traffic lights at a road junction, explains how a ROM might be programmed to operate a set of traffic lights. With the aid of a truth table and a circuit diagram, he goes into some detail. In this system a binary counter counting pulse supplied at regular intervals from a clock is used to provide a sequence of address inputs. Mike Meade checks the sequence above on a logic analyser. Shots of the analyser screen as he talks. Alan Reddish looks at a more complicated character display operated by sequential methods in which the ROM is rearranged so that row by row, column by column, or point by point scans will generate single alpha-numeric characters. An example of such a system, a Japanese - English electronic translator is demonstrated. Then, using an enlarged version of one character, David Gorham shows how economic this method is. Gorham goes on to explain, using a truth table, how the ROM for such a character display is organised. Mike Meade examines two methods by which an irregular sequence of signals can be generated for systems such as traffic lights where the various lights are lit for different, periods. The first method involves increasing the size of the ROM truth table and the capacity of the counter leading to repeated states in the ROM out put. The second method involves including a duration code in the ROM alongside the code which controls the lights. Meade shows that this is a much more economical way to approach the problem. He uses diagrams and the traffic lights model to illustrate his points. Alan Reddish summarises the programme.
Master spool number: OU 3384
Production number: FOUT057H
Videofinder number: 2646
Available to public: yes