Dragon Assembler, a simple assembler for a made-up microprocessor architecture
- 16-bit data bus.
- 12-bit address bus. Processor can address 4K of memory.
- 4 general purpose registers (GPR's). Will be expanded to 8 later.
- 4 special purpose registers: Program Counter (PC), Address Register (AR), Instruction Register (IR), FLAGS register. Stack pointer (SP) and stack-related operations (PUSH, POP, CALL, RET) will be added later.
Two addressing modes will be used:
- Register indirect: Uses the contents of a general purpose register as a pointer to a memory location(used by load/store instructions)
- PC relative: Adds the offset contained in the instruction to the contents of PC to obtain a pointer to a memory location (used by jump instructions)
Please scroll down for diagrams of the architecture.
Opcodes are 4 bits, and there are 16 different instruction types:
| Opcode (in hexadecimal) | Opcode Mnemonic | Instruction |
|---|---|---|
| 1 | LDI | Load Immediate |
| 2 | LD | Load |
| 3 | ST | Store |
| 4 | JZ | Jump if zero |
| 5 | JMP | Unconditional jump |
| 6 | Unused | Unused |
| 7 | ADD, SUB, AND, OR, NOT, XOR, MOV, INC, DEC | ALU operations |
| 8 | PUSH | Push to stack |
| 9 | POP | Pop from stack |
| A | CALL | Call a procedure |
| B | RET | Return from a proc. |
Later on, we will add the instructions PUSH, POP, CALL and RET to this list. Note that all these instructions require a stack, and therefore we have to implement a stack and a SP register before implementing them.
0.3.1
On the maintainer’s system(Make sure you have automake installed):
aclocal # Set up an m4 environment
autoconf # Generate configure from configure.ac
automake --add-missing # Generate Makefile.in from Makefile.am
./configure # Generate Makefile from Makefile.in
make distcheck # Use Makefile to build and test a tarball to distributeOn the end-user’s system:
./configure # Generate Makefile from Makefile.in
make # Use Makefile to build the program
make install # Use Makefile to install the program
dasm example.asmAsst. Prof. Mehmet Kadir Baran at Marmara University
for this magnificent educational material about Microprocessors and for giving Dragon Assembler a head start with his example source code for a simple assembler.
The MIT License (MIT)
Copyright (c) 2016 Mehmet Mert Yıldıran mert.yildiran@bil.omu.edu.tr
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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