Rhooti Smart Traffic Light Controller

CS 240 | Micro Architecture & Assembly Language | Cuesta College | Dr. Dube
8086 Assembly EMU8086 Virtual Device Collaborative Project

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Overview

An 8086 assembly program that simulates a fully operational 4-way smart traffic light controller using the EMU8086 Traffic Light virtual device. The controller manages a complete intersection across all four directions (North, South, East, West) and responds in real time to pedestrian crossing requests and emergency vehicle overrides.

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How It Works

The controller runs a continuous main loop cycling through six phases:

NS Green -> NS Yellow -> All Red -> EW Green -> EW Yellow -> All Red -> repeat

After every phase, the program performs a non-blocking keyboard check. If a flag is set, the program responds immediately without waiting through the next phase.

Modes

Mode	Trigger	Behavior
Normal Cycle	Automatic	Loops Green, Yellow, Red with timed delays
Pedestrian	P or p	Brief All Red flash, then extended EW Green for safe crossing
Emergency	E or e	Forces All Red immediately, holds for extended duration

BH Flag System

BH = 0   normal cycle
BH = 1   pedestrian waiting
BH = 2   emergency override

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Port & Bit Map

The program communicates with the traffic light hardware via Port 4 using the OUT instruction. The device uses a 12-bit layout across four sides of the intersection:

Side	Red	Yellow	Green
East	Bit 0	Bit 1	Bit 2
North	Bit 3	Bit 4	Bit 5
West	Bit 6	Bit 7	Bit 8
South	Bit 9	Bit 10	Bit 11

Hex States

NS Green  + EW Red    = 030Ch
NS Yellow + EW Red    = 028Ah
All Red               = 0249h
EW Green  + NS Red    = 0861h   (also used for Pedestrian)
EW Yellow + NS Red    = 0451h

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Non-Blocking Input

Keyboard input uses DOS service 06h with DL=FFh to check for a waiting key without halting execution. The timer never freezes.

MOV AH, 06h     ; direct console I/O, non-blocking
MOV DL, 0FFh    ; check mode: returns key if waiting, sets ZF if not
INT 21h         ; ZF set = no key, AL = key if pressed

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Procedures

Procedure	Description
MAIN	Main loop, phase sequencing, flag checks
CHECK_INPUT	Non-blocking keyboard read, sets BH flag
NS_GREEN	North-South green, East-West red
NS_YELLOW	North-South yellow, East-West red
ALL_RED	All directions red, safe transition state
EW_GREEN	East-West green, North-South red
EW_YELLOW	East-West yellow, North-South red
PEDESTRIAN_MODE	Extended crossing with All Red flash
EMERGENCY_MODE	Immediate All Red, extended hold

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Running the Project

1. Open EMU8086
2. Load Micro Traffic Light Procedure Project.asm
3. Open the Traffic Light virtual device under peripherals
4. Run the program
5. Press P or p for pedestrian crossing
6. Press E or e for emergency override

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License

BSD 3-Clause License. See LICENSE for details.