logic-gates/js/examples.js

// Pre-built example circuits
// Each example is a { gates, connections, nextId, camera } object

const W = 100; // GATE_W
const H = 60;  // GATE_H
const GAP_X = 160;
const GAP_Y = 100;

/**
 * SR Flip-Flop using cross-coupled NOR gates
 *
 *   S ──┐
 *       NOR─── Q
 *   ┌──┘  │
 *   │     │
 *   └──┐  │
 *       NOR─── Q̅
 *   R ──┘
 */
function srFlipFlop() {
    const gates = [
        // Inputs
        { id: 1, type: 'INPUT', x: 50, y: 80, value: 0, label: 'S' },
        { id: 2, type: 'INPUT', x: 50, y: 280, value: 0, label: 'R' },

        // Cross-coupled NOR gates
        { id: 3, type: 'NOR', x: 300, y: 80, value: 0 },
        { id: 4, type: 'NOR', x: 300, y: 280, value: 0 },

        // Outputs
        { id: 5, type: 'OUTPUT', x: 550, y: 80, value: 0, label: 'Q' },
        { id: 6, type: 'OUTPUT', x: 550, y: 280, value: 0, label: 'Q̅' }
    ];

    const connections = [
        // S → Top NOR input 0
        { from: 1, fromPort: 0, to: 3, toPort: 0 },
        // R → Bottom NOR input 1
        { from: 2, fromPort: 0, to: 4, toPort: 1 },
        // Top NOR (Q) → Bottom NOR input 0 (cross-couple)
        { from: 3, fromPort: 0, to: 4, toPort: 0 },
        // Bottom NOR (Q̅) → Top NOR input 1 (cross-couple)
        { from: 4, fromPort: 0, to: 3, toPort: 1 },
        // NOR outputs → visible outputs
        { from: 3, fromPort: 0, to: 5, toPort: 0 },
        { from: 4, fromPort: 0, to: 6, toPort: 0 }
    ];

    return {
        name: 'SR Flip-Flop (NOR)',
        description: 'Set-Reset latch using cross-coupled NOR gates. Toggle S to set Q=1, toggle R to reset Q=0.',
        gates,
        connections,
        nextId: 7,
        camera: { camX: 0, camY: 0, zoom: 1 }
    };
}

/**
 * SR Flip-Flop using cross-coupled NAND gates
 *
 *   S̅ ──┐
 *        NAND── Q
 *   ┌───┘  │
 *   │      │
 *   └───┐  │
 *        NAND── Q̅
 *   R̅ ──┘
 */
function srFlipFlopNand() {
    const gates = [
        // Inputs (active low for NAND SR)
        { id: 1, type: 'INPUT', x: 50, y: 80, value: 1, label: 'S̅' },
        { id: 2, type: 'INPUT', x: 50, y: 280, value: 1, label: 'R̅' },

        // Cross-coupled NAND gates
        { id: 3, type: 'NAND', x: 300, y: 80, value: 0 },
        { id: 4, type: 'NAND', x: 300, y: 280, value: 0 },

        // Outputs
        { id: 5, type: 'OUTPUT', x: 550, y: 80, value: 0, label: 'Q' },
        { id: 6, type: 'OUTPUT', x: 550, y: 280, value: 0, label: 'Q̅' }
    ];

    const connections = [
        // S̅ → Top NAND input 0
        { from: 1, fromPort: 0, to: 3, toPort: 0 },
        // R̅ → Bottom NAND input 1
        { from: 2, fromPort: 0, to: 4, toPort: 1 },
        // Top NAND (Q) → Bottom NAND input 0 (cross-couple)
        { from: 3, fromPort: 0, to: 4, toPort: 0 },
        // Bottom NAND (Q̅) → Top NAND input 1 (cross-couple)
        { from: 4, fromPort: 0, to: 3, toPort: 1 },
        // Outputs
        { from: 3, fromPort: 0, to: 5, toPort: 0 },
        { from: 4, fromPort: 0, to: 6, toPort: 0 }
    ];

    return {
        name: 'SR Flip-Flop (NAND)',
        description: 'Set-Reset latch using cross-coupled NAND gates. Inputs are active-low: set S̅=0 to set, R̅=0 to reset.',
        gates,
        connections,
        nextId: 7,
        camera: { camX: 0, camY: 0, zoom: 1 }
    };
}

/**
 * Gated D Latch (1-bit memory)
 *
 * Uses an SR flip-flop with gating logic:
 *   D ──AND──┐
 *   E ──┤    NOR── Q
 *   │   │ ┌──┘│
 *   │   │ │   │
 *   │   │ └──┐│
 *   E ──┤    NOR── Q̅
 *   D─NOT─AND┘
 *
 * When Enable=1, Q follows D.
 * When Enable=0, Q holds its value.
 */
function dLatch() {
    const gates = [
        // Inputs
        { id: 1, type: 'INPUT', x: 50, y: 100, value: 0, label: 'D' },
        { id: 2, type: 'INPUT', x: 50, y: 280, value: 0, label: 'EN' },

        // NOT gate to invert D
        { id: 3, type: 'NOT', x: 200, y: 340, value: 0 },

        // AND gates for gating
        { id: 4, type: 'AND', x: 350, y: 60, value: 0 },     // D AND E → S
        { id: 5, type: 'AND', x: 350, y: 340, value: 0 },    // NOT(D) AND E → R

        // Cross-coupled NOR gates (SR latch core)
        { id: 6, type: 'NOR', x: 550, y: 60, value: 0 },     // → Q
        { id: 7, type: 'NOR', x: 550, y: 340, value: 0 },    // → Q̅

        // Outputs
        { id: 8, type: 'OUTPUT', x: 750, y: 60, value: 0, label: 'Q' },
        { id: 9, type: 'OUTPUT', x: 750, y: 340, value: 0, label: 'Q̅' }
    ];

    const connections = [
        // D → AND top input, and D → NOT
        { from: 1, fromPort: 0, to: 4, toPort: 0 },
        { from: 1, fromPort: 0, to: 3, toPort: 0 },

        // E → both AND gates
        { from: 2, fromPort: 0, to: 4, toPort: 1 },
        { from: 2, fromPort: 0, to: 5, toPort: 1 },

        // NOT(D) → bottom AND
        { from: 3, fromPort: 0, to: 5, toPort: 0 },

        // AND outputs → NOR inputs (S and R)
        { from: 4, fromPort: 0, to: 6, toPort: 0 },
        { from: 5, fromPort: 0, to: 7, toPort: 1 },

        // Cross-coupling
        { from: 6, fromPort: 0, to: 7, toPort: 0 },
        { from: 7, fromPort: 0, to: 6, toPort: 1 },

        // Outputs
        { from: 6, fromPort: 0, to: 8, toPort: 0 },
        { from: 7, fromPort: 0, to: 9, toPort: 0 }
    ];

    return {
        name: 'D Latch (1-bit Memory)',
        description: 'Gated D latch — a 1-bit memory cell. When Enable=1, output Q follows input D. When Enable=0, Q holds its last value.',
        gates,
        connections,
        nextId: 10,
        camera: { camX: 0, camY: 0, zoom: 1 }
    };
}

/**
 * D Flip-Flop (edge-triggered, master-slave)
 *
 * Two D latches in series with inverted enable:
 * - Master latch captures D when CLK=0
 * - Slave latch outputs when CLK=1
 * This creates rising-edge triggered behavior.
 */
function dFlipFlop() {
    const gates = [
        // Inputs
        { id: 1, type: 'INPUT', x: 30, y: 100, value: 0, label: 'D' },
        { id: 2, type: 'CLOCK', x: 30, y: 350, value: 0, label: 'CLK' },

        // CLK inverter (for master latch)
        { id: 3, type: 'NOT', x: 170, y: 350, value: 0 },

        // === MASTER LATCH (enabled when CLK=0, i.e. NOT CLK=1) ===
        { id: 4, type: 'NOT', x: 170, y: 200, value: 0 },     // NOT D for master
        { id: 5, type: 'AND', x: 300, y: 60, value: 0 },      // D AND !CLK
        { id: 6, type: 'AND', x: 300, y: 240, value: 0 },     // !D AND !CLK
        { id: 7, type: 'NOR', x: 450, y: 60, value: 0 },      // Master Q
        { id: 8, type: 'NOR', x: 450, y: 240, value: 0 },     // Master Q̅

        // === SLAVE LATCH (enabled when CLK=1) ===
        { id: 9, type: 'NOT', x: 570, y: 200, value: 0 },     // NOT master Q for slave
        { id: 10, type: 'AND', x: 680, y: 60, value: 0 },     // masterQ AND CLK
        { id: 11, type: 'AND', x: 680, y: 240, value: 0 },    // !masterQ AND CLK
        { id: 12, type: 'NOR', x: 830, y: 60, value: 0 },     // Slave Q
        { id: 13, type: 'NOR', x: 830, y: 240, value: 0 },    // Slave Q̅

        // Outputs
        { id: 14, type: 'OUTPUT', x: 1010, y: 60, value: 0, label: 'Q' },
        { id: 15, type: 'OUTPUT', x: 1010, y: 240, value: 0, label: 'Q̅' }
    ];

    const connections = [
        // D → master AND, D → master NOT
        { from: 1, fromPort: 0, to: 5, toPort: 0 },
        { from: 1, fromPort: 0, to: 4, toPort: 0 },

        // CLK → NOT (invert for master)
        { from: 2, fromPort: 0, to: 3, toPort: 0 },

        // !CLK → master AND gates (enable)
        { from: 3, fromPort: 0, to: 5, toPort: 1 },
        { from: 3, fromPort: 0, to: 6, toPort: 1 },

        // !D → master bottom AND
        { from: 4, fromPort: 0, to: 6, toPort: 0 },

        // Master AND outputs → Master NOR (SR latch)
        { from: 5, fromPort: 0, to: 7, toPort: 0 },
        { from: 6, fromPort: 0, to: 8, toPort: 1 },

        // Master cross-coupling
        { from: 7, fromPort: 0, to: 8, toPort: 0 },
        { from: 8, fromPort: 0, to: 7, toPort: 1 },

        // Master Q → slave AND, Master Q → slave NOT
        { from: 7, fromPort: 0, to: 10, toPort: 0 },
        { from: 7, fromPort: 0, to: 9, toPort: 0 },

        // CLK → slave AND gates (enable, direct CLK)
        { from: 2, fromPort: 0, to: 10, toPort: 1 },
        { from: 2, fromPort: 0, to: 11, toPort: 1 },

        // !masterQ → slave bottom AND
        { from: 9, fromPort: 0, to: 11, toPort: 0 },

        // Slave AND outputs → Slave NOR (SR latch)
        { from: 10, fromPort: 0, to: 12, toPort: 0 },
        { from: 11, fromPort: 0, to: 13, toPort: 1 },

        // Slave cross-coupling
        { from: 12, fromPort: 0, to: 13, toPort: 0 },
        { from: 13, fromPort: 0, to: 12, toPort: 1 },

        // Outputs
        { from: 12, fromPort: 0, to: 14, toPort: 0 },
        { from: 13, fromPort: 0, to: 15, toPort: 0 }
    ];

    return {
        name: 'D Flip-Flop (Master-Slave)',
        description: 'Edge-triggered D flip-flop built from two D latches. Captures D on the rising edge of CLK. Use with the clock simulation to see it in action.',
        gates,
        connections,
        nextId: 16,
        camera: { camX: 0, camY: -50, zoom: 0.9 }
    };
}

// Export all examples as a list
export const examples = [
    srFlipFlop,
    srFlipFlopNand,
    dLatch,
    dFlipFlop
];

export function getExampleList() {
    return examples.map((fn, i) => {
        const ex = fn();
        return { id: i, name: ex.name, description: ex.description };
    });
}

export function loadExample(index) {
    if (index < 0 || index >= examples.length) return null;
    const ex = examples[index]();
    return {
        circuit: {
            gates: JSON.parse(JSON.stringify(ex.gates)),
            connections: JSON.parse(JSON.stringify(ex.connections)),
            nextId: ex.nextId
        },
        camera: ex.camera
    };
}