Free Simulator for 68HC12

Need to simulate the 68HCS12? You want the 68HCS12 simulator and (HTML based) textbook! You can use this one to get an idea of what the 68HCS12 simulator is like, but that simulator has more features and represents an entire rewrite of the user interface code. Alas, it isn't free.

A CD containing my 68HC12 textbook and an improved version of this simulator is also available here.


SIMHC12 is a simulator program for the Freescale/Motorola 68HC12. It simulates the M68HC12A4EVB evaluation board which contains an MC68HC812A4 microcontroller, 16k of external RAM and 32k of external ROM. The 68HC812A4 microcontroller simulation can run in Expanded Wide, Expanded Narrow, or Single Chip modes. SIMHC12 will also simulate the M68HC912B32 running in Single Chip mode.

Image of 68HC12 Simulator

The user has access to one serial port via a terminal emulator, as well as the Analog to Digital Converter, Timer Module (and Port T), Ports H and J (as well as D, A, and B depending on operating mode), IRQ, XIRQ, and the peripheral chip selects CS0 through CS3. The COP timer, internal RAM and EEPROM, and the full instruction set are implemented. Instruction timing is emulated, and clock stretch can be applied for all the chip selects.

A debugger is provided with the ability to step execution, step over subroutines, set any number of breakpoints, load S19 format files, and examine and modify registers and memory. The debugger is capable of stopping execution upon invalid memory accesses, uninitialized interrupt vector execution, and invalid instructions.

For version changes changes, look here.

SIMHC12 has been implemented in Java, and will run on any system having a Java interpreter, Version 1.1.7 or later. The Java Runtime (JRE) can be obtained for Microsoft Windows, Linux, and Sun Solaris operating systems at the Sun Java site.

Documentation is provided in HTML format, and can be viewed from within the simulator via an built-in HTML viewer (from IBM's Alphaworks).

SIMHC12 is copyrighted software. A free license is given for use in non-commercial or educational environments. The simulator has been used successfully in eight courses I've taught, but is no longer being developed (the 68HCS12 simulator, however, is). It will successfully run Motorola DBUG-12 and the EFORTH Forth interpreter. In any case, use at your own risk. Please report any bugs to me.

Download Here

Download SIMHC12 (453k) via HTTP

Stand out from the crowd and make a contribution toward my time to develop and maintain this program. Click below and donate via Paypal. You can charge to your credit card as well. Better yet, why not order the improved version with text here and get the textbook on CD as well?

Also available with an installer! The installer version are for Microsoft Windows 98 or later, or NT 4.0 or later. These will place icons to run SimHC12 in its various modes in the start menu or on the desktop. Note that if the icons are on the desktop, you can drag-and-drop S19 files onto the icon to start the simulator with that file. Very convenient for GUI-oriented users! These downloads are significantly bigger than the JAR file alone.

You only need to download the jar file above, or the executable below. Each download contains a copy of the simulator. In either case, you will need the Java runtime from I'm no longer distributing the free download with the Java Runtime because of the server bandwidth.

Download SIMHC12 with installer for Windows (1545k) HTTP