Acorn Electron

Acorn ElectronThe Acorn Electron is a slash down version of the BBC Micro and was released in 1983 by Acorn Computers Ltd. It has 32Kbytes RAM and BBC Basic V2.0 in its ROM along with the operating system. The Electron is easily expandable through an expansion port which helped the machine to be the third most sold machine in the UK. It has ports for cassette, RGB monitor, and RF TV, and the expansion port could easily attach disk drives, extra memory, more graphic tools such as teletext, and joysticks.

The Hardware of the BBC Computer was emulated by a single ULA chip which made the machine cheap to produce and very reliable. This ULA chip was designed by Ferranti in collaboration with Acorn, and due to the limitation of the chip, only one sound could be produced and not able to produce teletext video. Some models of Electron had a problem namely that after sometime, due to the heat generated by the ULA the chip in question tended to pop out of its socket making all sort of errors. This was solved in later models by placing a metal pressure plate so that the ULA Chip will stay in place.

The only drawback was memory access as in order to access the memory the ULA is able to provide 32K x 8 bits of addressable RAM but the electron uses 4164 chips which are 1-bit ram, forcing the ULA to do a two accesses to each chip instead of the traditional one time in the BBC Micro. This also forced video hardware to work the same way slowing down the video display of the Electron.
Electron
UK: £199 (1983)
21-ALA01-0001510
1983
MOS 6502A CPU running at a frequency of 1.79Mhz
32K Ram expandable to 64Kb and a 32Kb ROM containing Acorn Electron Basic + 6502 assembler.
Small Light Beige case with keyboard same colour and ports on the left and back side of case. The unit is very light and compact. The motherboard has few components due that it uses a ULA that does everything. The keyboard is a full QWERTY style and comfortable to type with. The case was designed by industrial designer Allen Boothroyd of Cambridge Product Design Ltd.
Custom ULA with Text resolution of
20 X 32,
40 x 25,
80 x 25,
80 x 32.
Graphics Resolution of
160 x 256 (4/16 colours)
320 x 256 (2/4 colours)
640 x 256 (2 colours) 8 Colours capable of flash mode which makes a total of 16 colours
The Sound is also controlled by the ULA capable of 1 channel of sound and 1 channel of white noise, 7 octaves it can also produce 3 virtual sound channels mapped to the single available channel for BBC software compatibility. All sounds are generated through a small internal speaker.
1 x Expansion Port
1 x Cassette Port
1 x RGB Port
1 x RF Port
1 x Composite Video Port
External Power Supply with a voltage of 18VAC 650mAh
Dimensions 160mm × 340mm × 65mm (W x L x H) Weight 300g
More than 1.5 million

The Club currently owns 2 units 1 is boxed complete with manuals, cables, software and power supply. The other unit only the manual and power supply are included, both units are fully functional and clean from scratch or dust.

Cassette Port

7 PIN Din 360

Female Chassis Mount
Pin Name Dir Desc
1 Cass OUT OUT Cassette MIC
2 GND N/A Ground
3 Cass IN IN Cassette Phones
4 Cass OUT OUT Cassette MIC
5 NC N/A No Connection
6 MOTOR CNT IN Cassette Remote
7 MOTOR CNT IN Cassette Remote
 

 

Composite Port

Phono Jack chassis female
Pin Name Dir Desc
1 SIGNAL OUT Video 1V PK-Pk
2 GND N/A Ground
 

 

DC Power Port

DC Power Jack

Female Chassis Mount
Pin Name Dir Desc
1 RET N/A AC RETURN
2 18V AC IN 18V AC Min 600mAh
 

 

Expansion Port

50-PIN Edge connector

Male (at the computer)
Pin Name Dir Desc
1 18V AC OUT 18V AC
2 18V AC OUT 18V AC
3 AC RET N/A AC RETURN
4 AC RET N/A AC RETURN
5 -5V OUT -5V DC
6 -5V OUT -5V DC
7 GND N/A GROUND
8 GND N/A GROUND
9 +5V OUT +5V DC
10 +5V OUT +5V DC
11 SND O/P OUT AUDIO OUT
12 16 MHZ OUT 16 MHZ CLOCK
13 DIV 13 IN IN Divide Signal by 13
14 CLOCK OUT Int CPU Clk 1.79 Mhz
15 /RESET IN RESET
16 /NMI IN Non-Maskable Int
17 /IRQ OUT Int Request
18 R-/W IN Read Write enable
19 D7 IN/OUT Data Bit 7
20 D6 IN/OUT Data Bit 6
21 D5 IN/OUT Data Bit 5
22 D4 IN/OUT Data Bit 4
23 D3 IN/OUT Data Bit 3
24 D2 IN/OUT Data Bit 2
25 D1 IN/OUT Data Bit 1
26 D0 IN/OUT Data Bit 0
27 RDY IN Hold Bus when active
28 NC N/A Not Connected
29 SLOT N/A Key
30 SLOT N/A Key
31 A15 OUT Address Bit 15
32 A14 OUT Address Bit 14
33 A13 OUT Address Bit 13
34 A12 OUT Address Bit 12
35 A11 OUT Address Bit 11
36 A10 OUT Address Bit 10
37 A9 OUT Address Bit 9
38 A0 OUT Address Bit 0
39 A1 OUT Address Bit 1
40 A2 OUT Address Bit 2
41 A3 OUT Address Bit 3
42 A4 OUT Address Bit 4
43 A5 OUT Address Bit 5
44 A6 OUT Address Bit 6
45 A7 OUT Address Bit 7
46 A8 OUT Address Bit 8
47 GND N/A Ground
48 GND N/A Ground
49 +5V IN +5V DC
50 +5V IN +5V DC
 

 

RF Port

Phono Jack

chassis female
Pin Name Dir Desc
1 SIGNAL OUT RF 75ohms
2 GND N/A Ground
 

 

RGB Port

6PIN DIN

Female Chassis
Pin Name Dir Desc
1 RED OUT Analogue RED
2 GREEN OUT Analogue GREEN
3 BLUE OUT Analogue BLUE
4 SYNC OUT Composite Sync
5 GND N/A Ground
6 +5V OUT +5V 500mA