|The Acorn 6502 Microcomputer Kit||The Acorn Microcomputer (1979)|
Timeline & people
Using the Monitor
This site has been created in order to preserve a piece
of computer history – Acorn Computer’s first public
offering, the Acorn Microcomputer (later known as the Acorn
System 1). The one pictured below was shipped on
9 April 1979.
In addition to describing the computer, I have written an Emulator for it – so you can try it for yourself even if you don't have the original hardware. You might find the emulator useful as an educational resource, too, as it really shows how to program a computer at the hardware level (and with the mini-debugger you can watch the registers and other internal state changing as instructions are executed).
Many thanks to Fabio Arpino for improving the images here.
The Acorn Keyboard
The computer was primarily sold as a kit; two Eurocard boards (160mm x 100mm) had first to be populated and wired together. These form a self-contained and unusually compact computer (for the time), needing only a 9-volt power supply. The visible (top) board is the Acorn Keyboard:
In addition to the white keyboard, this board also holds a
9-digit calculator-style 7-segment LED display (of which only
8 digits can be used) and, on the left, circuitry for the
cassette recorder interface (and a scan decoder).
In this picture the display is showing the contents of the memory location at address (A.) FE00, namely A0. This is the first byte of the firmware monitor program.
On the keyboard, the sixteen keys on the left provide for hexadecimal input values. The eight keys to their right initiate the following command functions:
The rst key resets the microprocessor, which starts the monitor program (which in turn initially displays eight dots, then waits for a command key to be pressed).
The Acorn Microcomputer
The lower board is the Acorn Microcomputer proper:
It holds (from left to right, top row):
The board was also marketed as a ‘Single Board Controller’ without the RAM and ROM chips.