Assembler Working 🔗

VR16 CPU Home Page

Well as the name suggests, this explains how the assembler works hehe.

1. assembler.py
   • Lines are first loaded onto a list from the asm source file.
   • Based on the opcode, a simple if condition is run and the proper extractor() is chosen.
   • Opcodes are only checked once the assembler reads start:, similarly exits the operation on seeing end:.
   • Once the extractor runs, the output is further sent back from extractor.py to this file and they’re written onto the .mem file
2. extractor.py
   • This file holds all functions based on opcode.
   • Essentially substrings the list given by assembler.py and converts into string representation of binary.
   • This is further sent back and written into the .mem file.
3. baseclass.py
   • Holds custom exceptions by subclassing Exception.
   • RegisterNotPresent and OpcodeNotPresent are two custom exceptions present at the moment.

General Syntax 🔗

1. All programs must start with the start: keyword and must end with end:.
2. Once start is initiliased, all instructions must be indented with spaces of 4.
3. All lines must end with the ; semicolon. This only applies to code once initialised.
4. Comments can made using the --.
5. Everything must be in lowercase.
6. Refer the instruction-set architecture for supported opcodes.

Registers Present 🔗

As mentioned, only 4 general purpose registers:

• r0
• r1
• r2
• r3

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