Nigel Orr- Underwater Acoustics Group wrote:

> So it seems... someone mentioned gpsim- I've not heard of it- do you have
> any more details?

gpsim is a software simulator for (primarily) PIC microcontrollers. It's
still in development, but it is distributed under GPL - in other words
it's doesn't cost anything (depending on how you measure cost) and the
source code is available. It is only a text-based command line
interface, however there is active discussion on the GNUPIC mailing list
for wrapping a gui around it.

So far, most of the infrastructure is in place for simulating PICs. The
major features include:

  o Breakpoints
    - Execution breakpoints
    - Register read breakpoints
      -- break if a specific value is read
      -- break if anything is read
    - Register write breakpoints
      -- break if a specific value is written
      -- break if anything is written
    - <CNTRL C> (break if control C is pressed; 0.0.6)

  o Execution
    - run
    - single step
    - multi-step
    - step over

  o Memory
    - dump all
    - dump range
    - modify a value
    - dump eeprom

  o Trace
    - gpsim traces every action taken

  o Stimuli
    - Synchronous bit stimulus (e.g. a clock)
    - Asynchronous bit stimulus (e.g. a serial data stream)
    - Asynchronous byte stimulus (not yet implemented)
    - I/O pin stimulus
      -- Input only
      -- bidirectional
      -- bidirectional with pull up
      -- open collector
    - Analog stimulus (not yet implemented)

  o Disassembler

  o Nodes
    - gpsim supports a node list (or if you wish a netlist)
      that allows you to connect two or more stimuli together

gpsim is designed to emulate more than one processor - though currently
only one is supported. Eventually the other 'processors' will include
LCD displays, A/D converters, etc.

gpsim is designed to be fast. On my 400 MHz pentium I can simulate a
20Mhz pic in real time!

Here's a dump of the gpsim's help:

gpsim> help
attach         Attach stimuli to nodes
break          Set a break point
clear          Remove a break point
disassemble    Disassemble the current cpu
dump           Display either the RAM or EEPROM
echo           echo "text"
help           Type help "command" for more help on a command
node           Add or display stimulus nodes
quit           Quit gpsim
run            Execute the pic program
step           Execute one or more instructions.
stimulus       Create a stimulus
trace          Dump the trace history
x              examine and/or modify memory


I currently support only the 16C84. This is because I'm still working on
the gpsim's infrastructure. However gpsim supports all of the c84's
peripherals: eeprom, wdt, tmr0, interrupts, I/O ports. The next release
will be 0.0.6 and will occur Monday or Tuesday next week. I will not
announce any releases to the PIC list though until the basic simulator
is complete. You'll have to lurk the gnupic mailing list if you want to
catch the announcements.

see
http://reality.sgi.com/jamesb/gnupic/
on instructions on how to join the gnupic mailing list.

Scott