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Connections

Connections define how signals flow between ports, instances, and constants.

Connect Block​

All connections must be inside a connect block:

connect {
    # Connection statements here
}

A component must have exactly one connect block.

Connection Syntax​

<source> -> <destination>;

The arrow -> indicates signal flow from source to destination.

Valid Sources​

  • Component input ports
  • Instance output ports
  • Constants
  • Bit-indexed or sliced versions of the above

Valid Destinations​

  • Component output ports
  • Instance input ports
  • Bit-indexed or sliced versions of the above

Connection Patterns​

Input to Instance​

A -> gate1.A;
B -> gate1.B;

Instance to Instance​

gate1.O -> gate2.A;
xor1.O -> and1.B;

Instance to Output​

gate2.O -> Result;
adder.Sum -> Sum;

Bit-indexed Connections​

DataBus[1] -> gate.A;      # Single bit
DataBus[8] -> gate.B;
gate.O -> Result[1];

Slice Connections​

Input[:4] -> LowNibble;    # Bits 1-4
Input[5:8] -> HighNibble;  # Bits 5-8

Constant to Instance​

MASK[1] -> and1.A;
Zero[{i}] -> gate{i}.B;

Complete Example​

component HalfAdder(A, B) -> (Sum, Carry) {
    xor1: XOR;
    and1: AND;
    
    connect {
        A -> xor1.A;
        B -> xor1.B;
        A -> and1.A;
        B -> and1.B;
        xor1.O -> Sum;
        and1.O -> Carry;
    }
}

Connection Rules​

Single Driver Rule​

Each input can only be driven by one source. This is invalid:

# ERROR: Two sources driving the same input
A -> gate1.A;
B -> gate1.A;  # Error!

Multiple Destinations​

A single source can drive multiple destinations:

A -> gate1.A;
A -> gate2.A;  # OK - A drives both gates
A -> and1.B;   # OK - fan-out is allowed

Connection Order​

The order of connections in the connect block does not affect behavior. Connections are evaluated concurrently, just like real hardware.

connect {
    # These are equivalent orderings:
    A -> xor1.A;
    B -> xor1.B;
    xor1.O -> Sum;
    
    # Same as:
    xor1.O -> Sum;
    B -> xor1.B;
    A -> xor1.A;
}