Introduction
SpinalHDL will check that all combinatorial signals which have impacts on the design are assigned by something.
Example
The following code :
class TopLevel extends Component {
val result = out(UInt(8 bits))
val a = UInt(8 bits)
result := a
}
will throw :
NO DRIVER ON (toplevel/a : UInt[8 bits]), defined at
***
Source file location of the toplevel/a definition via the stack trace
***
A fix could be :
class TopLevel extends Component {
val result = out(UInt(8 bits))
val a = UInt(8 bits)
a := 42
result := a
}