This is an assembler for a 16 bit alARM CPU written in rust.
Labels are strings that don't start with a #, $, %, or a number and don't contain white space or ;. Label definitions end with a :. Registers are defined with an R or r followed by the register number, for example R0 is register number 0. Immediate values can be in decimal, hexadecimal, or binary. Immediate values in decimal and start with a # or nothing, values in hexadecimal start with a $ or 0x, and values in binary start with a % or 0b. Immediate values are then followed by an optional - to indicate a negative number followed by the value. For example #15 is the number 15, 0x-12 is the number -18, and %101010 is the number 42. Comments start with a ; and end with a newline. Operations can be uppercase or lowercase and are defined in the table below. Rd, Rn, and Rm are registers and Im is an immediate value.
| Instruction | Description |
|---|---|
| NOP | No operation, does nothing |
| HALT | Halts the cpu, stops the clock |
| MOV Rd Rn | Moves the contents of Rn into Rd |
| LDF Rd | Moves the lower 4 bits of Rd into the flags |
| STF Rd | Moves the flags into the lower 4 bits of Rd |
| LDR Rd Rn Rm | Loads the contents of data memory located at an address defined by the contents of Rn plus the contents of Rm into Rd |
| LDR Rd Rn | Loads the contents of data memory located at an address defined by the contents of Rn |
| STR Rd Rn Rm | Loads the contents of Rd into data memory located at an address defined by the contents of Rn plus the contents of Rm |
| STD Rn Rn | Loads the contents of Rd into data memory located at an address defined by the contents of Rn |
| ADD Rd Rn Rm | Rd <- Rn + Rm + C (C = carry flag) |
| SUB Rd Rn Rm | Rd <- Rn - Rm |
| MUL Rd Rn Rm | Rd <- the lower 16 bits of Rn * Rm |
| MULU Rd Rn Rm | Rd <- the upper 16 bits of Rn * Rm |
| DIV Rd Rn Rm | Rd <- Rn / Rm |
| MOD Rd Rn Rm | Rd <- Rn mod Rm |
| AND Rd Rn Rm | Rd <- Rn bitwise AND Rm |
| OR Rd Rn Rm | Rd <- Rn bitwise OR Rm |
| EOR Rd Rn Rm | Rd <- Rn bitwise exclusive OR Rm |
| NOT Rd Rn | Rd <- bitwise not Rn |
| LSL Rd Rn Rm | Rd <- Rn logical shifted left by the lower 4 bits of of Rm |
| LSR Rd Rn Rm | Rd <- Rn logical shifted right by the lower 4 bits of Rm |
| ASR Rd Rn Rm | Rd <- Rn arithmetic shifted right by the lower 4 bits of Rm |
| ROL Rd Rn Rm | Rd <- Rn rotated left by the lower 4 bits of Rm |
| ROR Rd Rn Rm | Rd <- Rn rotated right by the lower 4 bits of Rm |
| CMP Rn Rm | Compares Rn Rm by subtracting Rn and Rm and setting the flags |
| B Im | Unconditional branch to PC + 1 + Im |
| BEQ Im | Branches to PC + 1 + Im if the zero flag is set |
| BNE Im | Branches to PC + 1 + Im if the zero flag is cleared |
| MOV Rd Im | Moves the immediate value Im into the register Rd |
To build from source, install Rust and run cargo build --release. An executable will be created under target/release/. You can run it with cargo run --release <source file> <object file> [-l], or just run the executable directly alarmas <source file> <object file> [-l]. <source file> is a path to an assembly source file, <object file> is a path to an object file that the assembler to write to, and the -l prints a listing to standard error.