The simulator (not all CPUs are supported) allows the user to show how their program will run. It gives a view of all the registers and how many CPU cycles have passed, along with the current instruction that executed and the next few in memory. To test the simulation, after assembling launchpad.asm type:
./naken_util launchpad_blink.hex
speed 1
run
This will load the laundpad_blink.hex file and set the CPU speed to 1Hz. The run command of course will start the simulation. To pause it just press Ctrl-C. To run in single step mode:
speed 0
run
One instruction is executed and the simulator breaks. Pressing enter or typing 'run' again will execute one more instruction. If there is a function needing to be profiled at location 0xf010, typing: call 0xf010 will execute it. The program will stop running at the RET of the function.
Three other useful commands are call, push, and set. To push something on the stack just do: push 0x1000 for example to push 0x1000 to the stack. To set the value of a register: set pc=1000 or set r5=0xffff. To call a function: call 0xf034 to call a function at location 0xf034. This pushes the return address 0xffff on the stack and sets PC to 0xf034. When the simulator sees PC==0xffff it returns back to you so the number of clock cycles it took to run the function.
There are 4 commands for reading and writing memory: bprint, wprint, bwrite, wwrite. So to write 5 bytes to location 0x1000, I could type:
It can confirm it's written by typing: bprint 0x1000
For reading and writing word sized data, wprint and wwrite work the same way.
As of March 16, 2014, I added a -run command to naken_util for MSP430. A program can now be assembled and then run directly from the command-line without entering the simulator:
naken_util -run program.hex
If when the program hits a ret instruction that didn't have a matching call instruction, the program will stop and the registers will be dumped along with number of cycles passed. This was added for automated testing in Java Grinder but could be pretty useful other places.
To assist with testing software there is a newer option "break_io" which allows the user to set an address as an I/O port that will exit the simulator if written so:
naken_util -msp430 -break_io 0x0000 -run program.hex
So now if the running program.hex does a mov.b #5, 0x0000 then the simulator exit with a return code of 5.