MU0ARM Assembler

This is a simple two-pass assembler for MU0ARM CPU Project @ Imperial

NOTE: ALU instructions are all floating point

Features

• Comments within assembly code
• Customizable opcodes for your own instruction set
• Use of .labels in assembly code (easier subroutine calls/loops)

How to Use

1. Download assembler binary and place in any directory.
2. Run the executable and it will generate a default config file named config.txt and one named input.txt in the same directory as Assembler.exe.
3. Type your assembly code into the input.txt and run the executable Assembler.exe again to generate the output file.

Examples

input.txt

LDR R1 R0 +15 wp; this is a comment
ADD R1 R0 LS3
SUB R0 R1
STP; stops the program

output.txt

Hex format:
0x100: 0x07FC	LDR R1 R0 +15 wp
0x101: 0x8418	ADD R1 R0 LS3
0x102: 0x9001	SUB R0 R1
0x103: 0x7000	STP

Binary Format:
0x100: 0b0000011111111100
0x101: 0b1000010000011000
0x102: 0b1001000000000001
0x103: 0b0111000000000000

Assembly Code Formatting

1. Load Store Instructions (default opcode: 0000) <OP> <Rd> <Rm> <n> <flags>; <comment>

   Mandatory Fields: OP, Rd, Rm Optional: n (default 0), flags (default 00), comment

   Examples:

   • LDR R1 R0 +15 wp

     • R1 := [R0 + 15] with post-increment (p bit)
     • R0 := R0 + 15 write-back (w bit)

   • STR R1 R0 -3 w

     • mem[R0 - 3] := R1
     • R0 := R0 - 3 write-back (w bit)

2. Program Counter Instructions (default opcodes: 0XXX, except 0000) <OP> <N>; <comment>

   Mandatory Fields: OP Optional: n (default 0), comment

   Examples:

   • JMP 12
     • Jump to location 12
   • STP
     • Stops the programs

3. Data Processing Instructions (default opcodes: 1XXX) <OP> <Rd> <Rm> <sh>; <comment> Mandatory Fields: OP, Rd, Rm Optional: shift n (default to LS0), comment

   Examples:

   • ADD R1 R0 LS2
     • R1 := R1 + R0 * 4
   • SUB R1 R0 RS2
     • R1 := R1 - R0 / 4

4. Using .labels Labels are used to make jumping to subroutines or loops much easier to code as you do not need to remember the memory address for the jump. For example, "JMP .loopstart" rather than "JMP 142".

   NOTE: Always type the .label as the first token on the line you want to jump to.

   Example code for loop program:

   LDR R1 R0 +1 wp 
   LDR R2 R0 +1 wp
   .loop SUB R2 R1
   CMP R2 R1
   JMI end; can directly reference label
   JMP loop; supports multiple labels
   .end STP
   

Planned Features

• Error Detection
  • Register or immediate number must be within bounds
  • Opcode typos