This page provides a (partial) emulator of the toy computer described in the book Programming a toy computer from scratch. The emulator starts with the toy computer's initial state, once fully assembled, but before any program is installed. To do anything useful with it you need to program it first, as described in the book. You can also install already existing programs, with the Load button (see the supplementary material of each chapter of the book for more details).
The black area emulates the screen of the toy computer (this requires WebGL2). The green part below it represents the Arduino Due board, with its L LED, and its RESET button. There is no ERASE button since you can simply reload this page to restart from a blank initial state. The Host section simulates a terminal on a host computer connected to the Arduino with a USB cable. It can be used install programs on the (emulated) Arduino (as described in the book).
This emulator emulates only a very small subset of the Arduino Due's microcontroller (an Atmel SAM3XE), and of the ARM Cortex M3 microprocessor it contains. Likewise, it only emulates a small subset of the RAiO RA8875 chip used to drive the LCD. These subsets only provide the features which are used in the book. Another important limitation is that, in case of a Hard Fault, the emulator stops with an error message, instead of executing the Hard Fault handler. In this case you need to reload the page to restart it.