It's necessary to take into account any simulation-significant changes which can be made by setting these fuse bytes and lock bits, i.e. size of the bootloader section, top border of the frequency value, restrictions for the LPM and SPM instructions.

This configuration mechanism is already partially implemented in the simulator for ATmega8/8A only. You may take a look at declaration of the functions to set fuse and lock bytes. They usually look like:

int MSIM_M8ASetFuse(void *mcu, unsigned int fuse_n, unsigned char fuse_v);
int MSIM_M8ASetLock(void *mcu, unsigned char lock_v);

and placed inside an MCU-specific header file (simm8a.h for ATmega8/8A). NOTE: Declarations of the functions are important!

It is important to let initialization mechanism know that these functions are available. You may achieve it defining macros with functions names:

#define SET_FUSE_F	MSIM_M8ASetFuse
#define SET_LOCK_F	MSIM_M8ASetLock

in the header file.

You may read datasheet (its Memory Programming section) to understand what modifications should be done in struct MSIM_AVR instance according to the fuse and lock bytes values provided.

These instructions (and others) usually use RAMPZ and RAMPD registers to be able to access other data segment in devices with more then 64KiB data space.

MCUSim has a separate issue tracker and a wiki located at trac.mcusim.org. You may visit it and list the active tickets by milestone.

There is a separate milestone called Patches Welcome which contains experimental features which could be useful to have. Please, pick up an issue or another one and let the mailing list ([email protected]) know which one it was.

If you don't know which issue to choose or feature to implement, just leave a short message at the mailing list anyway.

See datasheet for ATmega48A/PA/88A/PA/168A/PA/328/P:

• p. 27 (9. System Clock and Clock Options)
• p. 28 (9.2 Clock Sources)
• p. 30 (Table 9-4. Start-up Times for the Low Power Crystal Oscillator Clock Selection)
• p. 31 (Table 9-6. Start-up Times for the Full Swing Crystal Oscillator Clock Selection)
• p. 33 (Table 9-9. Start-up Times for the Low-frequency Crystal Oscillator Clock Selection and Table 9-10. Start-up Times for the Low-frequency Crystal Oscillator Clock Selection)
• p. 34 (Table 9-12. Start-up times for the internal calibrated RC Oscillator clock selection)
• p. 35 (Table 9-14. Start-up Times for the 128kHz Internal Oscillator and Table 9-16. Start-up Times for the External Clock Selection)

It could be worth to check size of program and data memory during MCU initialization process. There is a MSIM_M8AInit() function to initialize an instance of ATMega8A which could be a good point to start.

P.S. ATMega8A has 4K x 16 bits program (8192 bytes of flash) memory and 1120 bytes of data memory (96 bytes for register file and I/O memory and 1024 bytes for SRAM).

Why not track all issue here? While I am at it, you can also set-up discussion forum here.

HTHs.

It's required to make all missing I/O registers of ATmega8A microcontroller available to include into VCD dump.

You'll have to scan through datasheet http://www.atmel.com/Images/Atmel-8159-8-bit-AVR-microcontroller-ATmega8A_datasheet.pdf (page 380, 381), copy name of a register (MCUCSR for instance), try to find it in avrsim/include/mcusim/avr/sim/vcd_regs.h and add lines like this

• https://github.com/dsalychev/mcusim/blob/master/avrsim/include/mcusim/avr/sim/vcd_regs.h#L242-L244
  and this
• https://github.com/dsalychev/mcusim/blob/master/avrsim/include/mcusim/avr/sim/vcd_regs.h#L322

You may build and run avrsim as follows to print a list of registers available for VCD dump file:
./avrsim -p m8a -U flash:w:dhtc.txt --dump-regs=?
You'll see a new register in a list if you perform these steps described above correctly.

Please, feel free to ask me in case of any trouble or help required.

dhtc.txt

There is a BREAK command which is used by On-chip Debug system. It is intended to switch AVR MCU to the Stopped Mode to examine its internal resources. The AVRsim allows to do the same thing and is perfectly able to support it:

• AVRSim is executing commands loaded from a ROM file; MCU state is AVR_RUNNING;
• BREAK command is appeared; MSU state is switched to AVR_STOPPED; AVRSim is waiting for user input (if compiled with MSIM_TEXT_MODE) to continue.

There is a main() function - entry point for avrsim - placed in a file avrsim/avrsim.c. It has only a stub for parsing command line arguments at the moment. The stub uses POSIX getopt() function to parse the arguments passed to the application.

This task is to improve avrsim.c to parse parameters:

• m (example looks like avrsim -m m8a) to specify exact model of AVR microcontroller; avrsim.c should limit possible values for the parameter and select required microcontroller by calling specific initialization function (like MSIM_M8AInit())
• p (example looks like avrsim -p ~/avr-project/prog.hex); avrsim should check existence of the file and pass it to a function which loads AVR program memory (these functions are expected to be exist for each model of AVR microcontrollers, for instance MSIM_M8ALoadProgmem()

There is a test which performs a sequence of very similar actions (MCU initialization, program memory loading and simulating). It can be found at tests/avr_core_test.c.