A simple CPU written in java.

Right now it only directly executes assembly code.

It has 3 registers rA,rB,rC. Memory size is 0x0000 - 0xFFFF but can be expanded at will through the classes constructor or the CPU variable memSize.

The current instruction set:

nop: does nothing
hlt: halts the processor
add<r1><r2><r3>: adds r1 and r2 and places the result in r3
sub<r1><r2><r3>: subtracts r1 from r2 and places the result in r3
ldi<r1><v>: loads a value into the register/address
inc<r1><v>: increments the register/address by v
dec<r1><v>: decrements the register/address by v
jmp<adr>: jumps the program counter to an address/label
prt<r1>: prints the register/address to the output
prtf<r1>: prints the register/address value of the utf8 table to the output
bz<r1><adr>: branches if r1 is 0
bnz<r1><adr>: branches if r1 is not 0
bn<r1><v><adr>: branches if r1 is v
bnn<r1><v><adr>: branches if r1 is not v
ret: returns to the last branch or jump
shr<r1><v>: bitshifts the value in the register/address right by v
shl<r1><v>: bitshifts the value in the register/address left by v
mov<r1><r2>: copies the value of r1 into r2
and<r1><r2><r3>: AND's r1 and r2 and stores the result in r3
or<r1><r2><r3>: OR's r1 and r2 and stores the result in r3
xor<r1><r2><r3>: XOR's r1 and r2 and stores the result in r3
not<r1>: NOT's r1 and stores the value in that same register/address
call: jumps the program counter to an address/label

Additionally:

Labels are also supported, just create one by wrapping the name in [ ] (example: [start]) and reference it by just typing the name without the [ ] (example: jmp start). Comments can also be made with // in a new line or at the end of a line. Certain CPU specific values can be set via a . followed by their name and arguments (e.g. .memSize 0xFFFF). It is recommended to set them at the top of the prg file, although they should be able to be anywhere in the code.

The current list of CPU variables:

memSize: Specifies the memory size of the CPU (if not done before via the constructor). This can be either a normal integer (e.g. 65535 for 0xFFFF) or a hex number prefixed with a 0x.
sLabel: Sets the label from which the processor will start running code. All code before this label will be skipped if it is set. 

How to run:

The prg.txt file has an example program written in it. The CPU will execute the program in prg.txt by default.