PIC Emulator

This program is an emulator and debugger for a PIC16F74 microcontroller. Currently, the emulator supports all of the PIC16 instructions except SLEEP and CLRWDT. Peripherals such as the watchdog timer, other timers, and ADC are not supported. The debugger supports running, stepping forward, setting breakpoints, printing the contents of memory, writing arbitrary bytes to memory, manipulating single bits in memory, and triggering interrupts. Program usage and debugger commands are documented below.

Usage

pic_emu code.hex

The emulator uses as its input format Intel Hex files with each instruction taking up 2 bytes in little endian order. Hex files like this can be produced from PIC assembly code using the GNU PIC assembler (gpasm) from the GNU PIC utilities package.

Debugger Commands

A note on integers

Several of the commands take integer arguments. By default, the arguments given will be parsed as signed decimal integers. However, you can specify unsigned hex numbers by appending h to the end, as you do in the PIC assembler. So 11h is decimal integer 17.

Controlling Execution

run - Resets the processors and begins executing instructions starting from instruction 0. Continues until an error occurs, the program terminates normally, or a breakpoint is reached. This command has an abbreviation r.

continue - Resumes executing instructions from the current processor state and continues until an error occurs, the program terminates normally, or a breakpoint is reached. This command has abbreviation c.

int - Triggers an interrupt. When this command is run, the GIE bit of the INTCON register is checked. If it is set, the current value of the program counter is pushed onto the stack and pc is changed to the interrupt vector (address 4). The GIE bit in the INTCON register is also cleared.

step - Executes a single instruction and then returns control to the user. This command has the abbreviation s.

Breakpoints

break addr - Set a breakpoint at the given instruction address. This command has abbreviation b.

delete addr - Removes the breakpoint at the given instruction address. This command has abbreviation d.

Accessing memory

Note - Addresses given to commands in the debugger are always absolute addresses. That is, they are not affected by banking.

print addr - Prints the contents of data memory at the given address. The address argument can also be one of three special values, "pc" for the program counter, "w" for the accumulator register, or "tos" for the top of the instruction stack. This command has abbreviation p.

put addr value - Writes the given value to memory at the given address.

set addr bit - Sets the given bit in the byte at the given address. The bits are labeled little endian (so bit 0 is the LSB and bit 7 is the MSB).

clear addr bit - Clears the given bit in the byte at the given address.

flip addr bit - Flips the given bit in the byte at the given address.