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Scope violation

Introduction

SpinalHDL will check that there are no signals assigned outside the scope they are defined in. This error isn’t easy to trigger as it requires some specific meta hardware description tricks.

Example

The following code:

class TopLevel extends Component {
  val cond = Bool()

  var tmp : UInt = null
  when(cond){
    tmp = UInt(8 bits)
  }
  tmp := U"x42"
}

will throw:

SCOPE VIOLATION : (toplevel/tmp :  UInt[8 bits]) is assigned outside its declaration scope at
  ***
  Source file location of the tmp := U"x42" via the stack trace
  ***

A fix could be:

class TopLevel extends Component {
  val cond = Bool()

  var tmp : UInt = UInt(8 bits)
  when(cond){

  }
  tmp := U"x42"
}