For another viewpoint on the MK14, see here.
Science of Cambridge
Micro Computer Kit
The MK14 is a kit of parts assembled by the user to form a minimum cost computer. It comprises in miniature the essential elements common to all computer systems.
Central Processor Unit
Communication with, and programming the machine, takes place through a simple keyboard and display. The most fundamental language - machine code condensed into hexadecimal notation is utilised. Thus the system can be used as an educational tool, or for the purposes of the professional who has a need for a computer on the desk or bench top.
All the integrated circuits and components required are included in the kit. Also provided are a printed circuit board and a comprehensive handbook describing construction, operation, and use. Since the unit is primarily a computer it is designed not exclusively for the electronics expert, but for anyone wishing to experiment practically with the essence of digital computation.
Elementary competence in soldering and printed circuit assembly is needed, but carefulness and a methodical approach are the main requirements.
Central Processor Unit
The C.P.U. is a National Semiconductor SC/MP microprocessor. It is suited to an ultra simple configuration because although it functions without additional circuits it has a general purpose architecture allowing system expansion.
Instruction types also conform with the general purpose computer area, while special instructions and architectural features such as delay timer and built in serial and parallel input and output are particularly convenient in a compact unit.
Fixed Memory and User Terminal
512 words of permanent memory contain a monitor programme which provides the user with instant control following switch on. By entering commands and data via the keyboard and observing internal status and programme results on the display, complete control and supervision is achieved.
Any part of memory or input/output port can be examined and written to. All C.P.U. programmer registers ie. Accumulator, Extension, Status, Programme Counter and the three Memory Pointers are overseen in the same way. Execution of a users programme can be started from any chosen location and break-points (stops) may be inserted allowing the user to analyse the progress of his programme.
The keyboard and display possess a dual function the users programme is able to utilise them for its own purposes.
256 words of write-able memory are included in the basic package. Keyboard commands allow loading or examination of computer instructions and data in the same sequence as the C.P.U itself uses. Thus, this part of memory is where the user enters, and experiments with, his own programmes. Note : some twenty words in this area are devoted to the monitor function.
Provision exists on the printed circuit for extending memory by two blocks of 256 words and 128 words respectively (see input/output description)
In order to satisfy the need for responding to external commands and information, and for controlling external circuits, a number of logic inputs and outputs are incorporated with expansion capability. The basic unit possesses an interrupt or data input, a data input, three signal outputs, a serial input and one serial output.
Provision is made on the printed circuit board for the optional addition of 15 lines of input/output. Each line is individually selected by the users programme to function as an input or an output. (This is part of the same device providing 128 words of additional memory).
The manual consists of five main sections.
Tape Interface kit with software and instructions. A low cost interface to any cassette recorder.
Prom Programmer for DM 74LS571 directly driven from the MK14 and needing only an extra twelve volt supply, this allows the user to programme fusible link proms with his own operating system which can replace the existing monitor.
Revised Monitor programme in 2 x DM 74LS571 - a condensed version of the existing operating system but including sub-routines for tape interface - load and dump, single step and offset calculation, and having single keystroke data entry. (This can only be supplied as an extra as the manual refers to the standard monitor).
The handbook is designed to enable the non-specialist without prior electronic or software knowledge to get to grips with computing as well as to satisfy the need of the better informed for a basic user manual.
Science of Cambridge Ltd.
6 King's Parade, Cambridge CB2 1SN. Telephone Cambridge (0223) 311488