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Assignment overlap

Introduction

SpinalHDL will check that no signal assignment completely erases a previous one.

Example

The following code

class TopLevel extends Component {
  val a = UInt(8 bits)
  a := 42
  a := 66 // Erase the a := 42 assignment
}

will throw the following error:

ASSIGNMENT OVERLAP completely the previous one of (toplevel/a :  UInt[8 bits])
  ***
  Source file location of the a := 66 assignment via the stack trace
  ***

A fix could be:

class TopLevel extends Component {
  val a = UInt(8 bits)
  a := 42
  when(something) {
    a := 66
  }
}

But in the case when you really want to override the previous assignment (as there are times when overriding makes sense), you can do the following:

class TopLevel extends Component {
  val a = UInt(8 bits)
  a := 42
  a.allowOverride
  a := 66
}