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Width mismatch

Introduction

SpinalHDL will checks the correctness of signals bitwidth on assignements and on operators inputs.

Assignement example

The following code :

class TopLevel extends Component {
  val a = UInt(8 bits)
  val b = UInt(4 bits)
  b := a
}

will throw :

WIDTH MISMATCH on (toplevel/b :  UInt[4 bits]) := (toplevel/a :  UInt[8 bits]) at
  ***
  Source file location of the OR operator via the stack trace
  ***

A fix could be :

class TopLevel extends Component {
  val a = UInt(8 bits)
  val b = UInt(4 bits)
  b := a.resized
}

Operator example

The following code :

class TopLevel extends Component {
  val a = UInt(8 bits)
  val b = UInt(4 bits)
  val result = a | b
}

will throw :

WIDTH MISMATCH on (UInt | UInt)[8 bits]
- Left  operand : (toplevel/a :  UInt[8 bits])
- Right operand : (toplevel/b :  UInt[4 bits])
  at
  ***
  Source file location of the OR operator via the stack trace
  ***

A fix could be :

class TopLevel extends Component {
  val a = UInt(8 bits)
  val b = UInt(4 bits)
  val result = a | (b.resized)
}