up or down, the low-quality tapes used may have 'drop ins' or 'drop outs' (magnetic blobs, holes etc.), the tape speed may vary significantly and if fitted with AGC, the tape recorder can distort data when sudden signal transi- tions are encountered. Different methods of storage have been produced by industry and the amateur fraternity in the States, but many have inherent problems. R Smith of Essex University showed his method whereby recording relies on transitions rather than polarity of signals, giving good hardware and noise independence. The system is synchronized at the character level to permit partial recovery of corrupted data and it is block structured to allow data larger than the micropro- cessor memory to be processed.

D Courteney of Queen's University, Belfast, explained how a colour tele- vision with teletext decoder could be interfaced to a microprocessor. Provi- ded high resolution was not required, the system provides a cheap means of colour graphics/alphanumerics output.

System costs moved up a lot when Robin Hodgson of Motorola described a heating/ventilating controller based on an M6800 and installed at their Toulouse factory. Relative annual energy savings with the new system were estimated at 40%, but as one dele- gate rightly pointed out, the original pneumatic logic controller it replaced had not been designed for maximum efficiency in the first place, so the actual benefits were harder to calcu- late.

Commercial greenhouse control was the next application. P S Vincent of the National Institute of Agricultural Engineering (NIAE) detailed the dev- elopment of a system which monitored and controlled the heating and venti- lation. M6800-based too, the unit had been built from a family of micro- processor cards developed within the NIAE to suit general-purpose applica- tions. New component introductions had dated this family since its design in 19-/6, but the number of proiects it had been used in meant a significant reduction in development times.

Two contributions from the British Post Office described the 8080 micro- computer coin and fee checkingsystem designed to replace electronically the

traditional units. The second paper described the complex distributed pro- cessing system ACRE (austomatic call recording equipment). This 8080-based system simplifies the telephone opera- tors' task by eliminating the need for the old system of mechanical timing and hand-written call tickets. To get the high reliability (minimum MTBF of 50 years) that the Post Office de- mand, each control unit is duplicated, and additionally, the software allows the operator to take manual control if necessary. The programming has been based on PLM, which is a block- structured language allowing the Post Office to use structured programming techniques. Mike Robards estimated that around 20 manyears of develop- ment had gone into the software, but as the project dates back to 1973 some of the early work was spent on producing their own debugging aids and software.

Other applications included a chro- matographic signal analyser from Dr Mackenzie of Philips Research Labora- tories, Redhill and a foetal heart monitor from Liverpool University and University Hospital Nottingham for which the software was developed entirely in machine code[

Copies of the proceedings are available, price £8. Contact SERT, 8-10 Charing Cross Road, London WC2H 0HP.

Barrie Nicholson

The and

microprocessor its application

5-16 September 1977, University College, Swansea, UK, sponsored by Science Research Council under the auspices of CREST-ITG

The course, which was directed by David Aspinall and organized by John Mason, aimed to review the hardware and software constituents of microprocessor systems and to provide

first hand experience of microproces- sors project management. To achieve these objectives, the course was divided into the following sections

• Microprocessor hardware compon- ents 12 sessions

• Microprocessor software techniques 11 sessions

• Microprocessor project management 4 sessions

• Microprocessor design project 12 sessions

• Special lectures 4 sessions

Most of these sections, along with tutorial sessions, ran for the entire duration of the course.

There were around 40 participants, all having previously experienced infor- mation-processing systems to some extent, from several different countries. Most of the participants were either computer scientists or electronic engineers, from both industrial and educational establishments. The lec- turers, who also came from various backgrounds, were

• David Aspinall (UK) Microprocessor hardware components

• lann M Barron (UK) Special lectures • Wesley A Clark (USA) Micropro-

cessor hardware components • David Dack (UK) Microprocessor

design project • Erik L Dagless (UK) Microproces-

sor hardware techniques • Roy D Dowsing (UK) Microproces-

sor software techniques • Tony R Hoare (UK) Special lectures • John K Iliffe (UK) Microprocessor

software techniques • Carol A Ogdin (USA) Microproces-

sor project management • Marco Vanneschi (Italy) Micropro-

cessor hardware components

Andrew T Colin (UK), who was to have lectured in the microprocessor soft- ware techniques section, was unable to attend.

Wes Clark opened the microproces- sor hardware components sessions with a short overview of the rapid evolution of digital electronic technol- ogy. He illustrated how inexpensive some of today's digital systems can be by passing round a light-sequence gen- erator and then dramatically smashing

vol 1 no 8 december 77 501

it to pieces with a hammer! After this opening, he began to build up a picture of how today's LSI circuits are devel- oped, discussing the characteristics of semiconductors, logical elements, their interconnection and packaging. Erik Dagless described the characteristics of various fixed-instruction-set microcom- puters, with the field of microprogram- mable microcomputers being covered by Marco Vanneschi. David Aspinall completed the sessions with a descrip- tion of how several inexpensive micro- processors can be used in a network to realize a sophisticated computer sys- tem.

The sessions on microprocessor software techniques were opened with Roy Dowsing stressing the need for good software management. He went on to cover such topics as logical design, implementation, simulation, testing and optimization. Iohn Iliffe discussed, in some detail, the merits of interpretive machines, implemen- ted using microprogrammable proces- sors. lann Barron and Roy Dowsing described the languages used at present by microcomputer designers and con- cluded by highlighting their limita- t ions-the uniqueness of assembly languages and the unsuitability of to- day's prevalent high-level languages.

The importance of good project organization was emphasized by Carol Ogdin in the microprocessor project management sessions. A disciplined approach to the design tasks, with the aid of a rigorous documentation scheme (documentation should be the

aim of a project-a prototype merely the proof), was proposed. She went on to discuss the skills required of a com- petent design team, remarking that successful microprocessor engineers must be equally conversant with hardware and software. The value of hardware and software development aids was stressed and several com- mercial systems were described.

It was Dave Dack's idea to set the course participants a real microproces- sor design project. The aim of the pro- ject was for teams, each consisting of three participants, to produce an effective design for a power meter. Such factors as selftest, reliability, ease of use and documentation were stressed to be important features of the pro- ject. Half the teams used the 8008 and half the 8080. Reasonable micro- processor laboratory facilities were provided, including several small de- velopment systems and crossassemblers for both microprocessors. Almost everyone was engrossed in this rather captivating project. Prizes were award- ed to the teams who produced the best overall design using each type of micro- processor; presentations of the winning designs were made to all the course participants.

The future development of micro- computers was discussed by lann Barron in one of the special lectures. He predicted that the microcomputer manufacturers would not change their attitudes to the development of microcomputers in any significant man- ner, but would simply continue to try

to produce more complex processors on each integrated circuit and begin to move towards some kind of standard- ization. He saw that this trend, coupled with a declining market for the larger computers, would lead to much higher competition in the microcomputer industry and so microcomputer manu- facturers would have to exploit all possible high-volume applications in order to survive, lann Barron conclu- ded by intimating that such an environ- ment would not allow an optimum microcomputer to ew)lve readily. He suggested that an optimum microcom- puter might be a small computer, con- sisting of several microprocessors lin- ked serially in a multiprocessor net- work, using English as a language. Tony Hoare discussed the advantages of multiprocessor systems over a single large processor for solving prob- lems concurrently. He went on to des- cribe a simple language designed to extract maximum benefits trom multi- processor systems. It was also suggested that this approach may even be valuable as an initial design procedure in pro- gramming conventional computers. A lecture was given by Terry Robbins, preceding a visit around the BP Chemi- cals' Baglan Bay plant, giving an ex- ample of how comp.uters can handle in- formation from many difficult sources to give management more accurate in- formation on which to base decisions.

lan ]ohnson and Puul I l~rney Chelsea Coflege University of London

m Place ytmr ati in

For detai ls contac t L l oyd Col l ins on 01-261 8 7 5 7 / 8 7 4 3

502 microprocessor~