|The Acorn 6502 Microcomputer Kit
|Acorn Microcomputer Emulator
Timeline & people
Using the Monitor
These pages describe the Emulator for the Acorn 6502
Here you will find:
If you discover any problems with the Emulator, please send me e-mail describing the problem.
The Acorn System 1 Emulator is a program which runs under Windows and emulates the hardware of the real micro-computer. Part of the Emulator mimics the function of the 6502 processor and its associated integrated circuits (the RAM-I/O chip, and the RAM and ROM), and the remainder provides the user interface, which simulates the LED display, the keyboard, and the tape cassette interface.
The Emulator runs the original Acorn monitor program, and so allows the development of programs exactly as on the original machine. The intent is to preserve the general look and feel (and sound) of the original, while making it available to many more people than have the actual hardware. The Acorn design is an excellent platform for learning the basic concepts of computers and the skills necessary to program a computer using machine code.
In addition to the functions of the original Acorn kit, the Emulator provides:
The Emulator is a program for Windows and should run on Windows 95 or any later version (it has only been tested on Windows 98 and Windows 2000, however – please let me know of any problems on other versions). A 32MHz or faster processor is required.
My employer, IBM, has kindly given me permission to make the Emulator for the Acorn 6502 Microcomputer Kit available on this website. The Emulator software is distributed free of charge under the conditions of the IBM Employee-Written Software program. If you download or use the Emulator you agree to the terms in the IBM License Agreement for Employee-Written Software. Please read it before downloading.
Download the acornEmulator.zip file from this link. The zip file contains two files, the acornEmulator.exe program and IBMlicense.txt (which must always accompany the program).
Unzip the zipfile into a known location and then start the program from a command line or by clicking its icon from an Explorer Window. You can create a shortcut icon for it on your desktop by right-clicking on its icon and using Send To > Desktop.
On starting the emulator for the first time, you should see a window with a menu bar and a representation of the Acorn LED display and keyboard. (The display is relatively large, to make it more readable, but the buttons and labels are laid out as on the real Acorn keyboard and to scale within the window.) You can change the size of the window by pressing the + or - keys to increase or decrease the size. Alternatively, you can drag its width with the mouse; the window will then ‘snap’ to the largest size which will fit in that width.
On startup, the emulator is in the same state as the real hardware after power has been switched on. The ROM is loaded with the monitor, RAM has random values, the RAM-I/O outputs are all high, and the processor is halted. All display digits (simulated LEDs) should therefore be dark, except the right-hand digit which should have all its segments lit.
To start the monitor running, click on the rst (reset) button on the Acorn keyboard, or press the Escape (Esc) key on your PC keyboard. You should then see the initial pattern (eight dots) displayed by the monitor.
For further information on using the monitor, see the guide for Using the Acorn Monitor.
The emulator stores various information (such as screen position and size) in a file called as1.ini, which is placed in the same directory as the program file.
The most obvious difference from the real machine is the LED display area, which is presented using a scaled font instead of attempting to mimic the appearance of the real ‘calculator’ display, which looks like this:
There are some more subtle differences, however: