Electron Specifications

The Electron's central processing unit is a 2 Mhz 6502 microprocessor.
64K bytes of memory are provided: a 32k ROM containing the Machine Operating System and BASIC interpreter, and 32k of RAM.

About 3.5k of RAM is required by the Machine Operating System; the remainder is available for the high resolution graphics display and user programs.

The Electron provides a colour television signal for connection to a normal domestic television via its aerial socket. The signal, available through a phono connector, is 625 line, 50 Hz, PAL colour encoded, modulated on UHF channel 36. A two metre lead is supplied with the machine.

A DIN connector provides an R/G/B/sync output at TTL levels for direct drive to a colour monitor.

A second phono connector provides output for a composite video monitor.

Seven display modes are available, providing differing text and graphics resolutions and simultaneous colour availability, and using differing ammounts of RAM. The details of the modes are summarised below;

Mode 0 640x256 graphics, 80x32 text, 2 colours, (20k RAM used)
Mode 1 320x256 graphics, 40x32 text, 4 colours, (20k RAM used)
Mode 2 160x256 graphics, 20x32 text, 16 colours, (20k RAM used)
Mode 3 80x25 Text Only, 2 colours, (16k RAM used)
Mode 4 320x256 graphics, 40x32 text, 2 colours, (10k RAM used)
Mode 5 160x256 graphics, 20x32 text, 4 colours, (10k RAM used)
Mode 6 40x25 Text Only, 2 colours, (8k RAM used)

The colours available are; black, white, red, green, yellow, blue, magenta and cyan.
In addition eight flashing colours can be chosen.

A full character set is provided, including upper and lower case characters with genuine descenders.

Additional text characters can be defined by the user. Text and graphics can be freely mixed, and user defined characters can be placed anywhere on the screen, not just at the normal text positions.

Seperate or overlapping text and graphics windows can be defined by the user over any area of the display. Each window can be filled seperatly, and text may be scrolled up and down within the text window.

A number of software facilities are provided to simplify graphics production, including line drawing and filling aread with colour. In particular, very rapid colour changes are possible using the pallette.

External Storage
The electron can be connected to most standard audio cassette recorders or the BBC Data Recorder to record programs for permanent storage, and to load existing programs into the Electron's memory. The computer provides full automatic motor control, so that when used with a cassette recorder with an external motor control facility the tape will stop automatically at the end of a file. The connection is via a 7-pin DIN socket, and transmission is at 1200 baud using the computer user's tape standard tones.
The BASIC interpreter is identical to that implemented in the highly sucessful BBC Microcomputer. Certain hardware features of the BBC Micro are not provided by the Electron, so a small number of statements do nothing when included in Electron programs.

BBC BASIC closely follows the Microsoft standard, but has many powerful additional features. These include;

Long variable names
Interger, floating point and string variables
Multi-dimension interger, floating point and string arrays
Many string handling facilities
Local variables
Multi-line interger, floating point string functions
Full recursion on all functions and proceedures
Facilities for loading and saving of programs and data on cassette
Facilities for effective error trapping and handling

A number of facilities are provided to simplify use of the Electron's full colour graphics and to enable sound generation using the internal loudspeaker.

In addition, the BASIC interpreter includes a 6502 assembler, enabling BASIC statements to be freely mixed with 6502 Assembly Language.

The Electron has a 56 key full travel QWERTY keyboard. There are ten user definable keys, and 29 pre-defined keys enabling BASIC keywords to be entered in a single keystroke. Each key has auto-repeat, and the keyboard has two key roll over and debounce.
An internal loudspeaker is provided driven from a single channel sound circuit. It is controlled via four software channels, and facilities provided by the BASIC interpreter enable simple sound synthesis to be achieved.
An interrupt driven event timer is provided within the Machine Operating System which can be used as an elapsed time clock. It allows real time control and timing of user's responces to be incorporated in programs.
Power Supply
The Low voltage input required for the Electron's internal power supply is provided from a transformer conveniently incorporated into the plug which is supplied with the machine. A three metre cable links the electron to the transformer.
Expansion Units
A multi-way connector is provided at the rear of the basic microcomputer for the addition of expansion units containing interfaces to additional hardware. Expansion units will have a similar connector allowing any combination of units to be used with a single machine, and each unit will connect securely to its host by means of finger-tightened screws.

Source of Information : Acorn Electron Brochure.

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