sim8085 — 8085 Assembler + Simulator (lab-friendly)

sim8085 is a lightweight 8085-ish assembler + interactive simulator built to run classic microprocessor lab programs from this repo:

• src/school/*.asm
• src/personal/*.asm

It’s designed to be:

• ✅ Easy to understand
• ✅ Great for learning / teaching
• ✅ Hackable and extendable
• ✅ Perfect for running real 8085 lab sheets

This is an instruction-level simulator (not cycle-accurate). It focuses on executing the logic of programs correctly rather than emulating exact machine timings.

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✨ Features

• Interactive terminal REPL
• Loads existing .asm templates from this repo
• Label support (LOOP:, JNZ LOOP, etc.)
• Simulated registers: A B C D E H L, SP, PC
• Flags: S Z P CY
• Full 64KB memory space
• Breakpoints, stepping, memory inspection
• Designed around real 8085 lab exercises

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🚀 Quick Start

From the repo root:

python simulator/main.py

You should see:

8085>

🧪 Using the bundled .asm templates

List available templates:

8085> templates

Load a program by fuzzy-matching its filename:

8085> loadtpl school bubble

Seed memory:

8085> setmem 7050H 0AH

Run until HLT:

8085> run

Inspect registers:

8085> regs

Inspect memory:

8085> mem 7050H 40

🧠 Example: Bubble Sort Demo

Bubble sort expects:

• 7050H = size
• 7051H.. = array data

Example session:

8085> loadtpl school bubble
8085> setmem 7050H 0AH
8085> setmem 7051H 09H
8085> setmem 7052H 02H
8085> setmem 7053H 0AH
8085> setmem 7054H 01H
8085> setmem 7055H 07H
8085> setmem 7056H 03H
8085> setmem 7057H 08H
8085> setmem 7058H 04H
8085> setmem 7059H 06H
8085> setmem 705AH 05H
8085> run
8085> mem 7051H 0A

After running, memory block 7051H..705AH will be sorted.

🧾 REPL Commands

load <path>                 Load an .asm file
templates                   List available templates
loadtpl <school|personal> <name>
run [max_steps]             Run until HLT or breakpoint
step [n]                    Step instruction(s)
regs                        Show registers and flags
mem <addr> [len]            Dump memory
setmem <addr> <byte>        Write memory byte
bp <addr>                   Toggle breakpoint
bps                         List breakpoints
pc <addr>                   Set PC
reset                       Reset CPU and memory
help                        Show help
quit                        Exit

🧩 Supported Instruction Subset

Data movement

• MOV, MVI, LXI
• LDA, STA
• LHLD, SHLD
• LDAX, STAX
• XCHG

Arithmetic / logic

• `XRA, ADD, ADC, ADI
• SUB, SBB, SUI
• ANI, CMP, CPI
• `INR, DCR
• DAA, CMA

Rotate / flags

• RRC, RAR, RLC
• STC, CMC

16-bit / pointers

• INX, DCX, DAD

Control flow

• MP, JZ, JNZ, JC, JNC
• CALL, RET
• HLT

Assembler features

• Labels (LOOP:)
• ORG directive (optional, assembler-dependent)

🛠️ Extending the Simulator

Opcode execution lives in:

bash
simulator/sim8085/cpu.py

Add new instructions by extending the _exec() dispatcher. The assembler lives in:

bash
simulator/sim8085/assembler.py

🗂️ Project Structure

src/
  school/        # School lab programs
  personal/      # Personal practice programs

simulator/
  main.py        # Entry point
  sim8085/
    assembler.py # Parser / label resolver
    cpu.py       # CPU + memory + flags
    repl.py      # Interactive terminal

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