Description

The UInt/SInt type corresponds to a vector of bits that can be used for signed/unsigned integer arithmetic.

Declaration

The syntax to declare an integer is as follows: (everything between [] is optional)

Syntax Description Return
UInt[()]
SInt[()]
Create an unsigned/signed integer, bits count is inferred UInt
SInt
UInt(x bits)
SInt(x bits)
Create an unsigned/signed integer with x bits UInt
SInt
U(value: Int[,x bits])
S(value: Int[,x bits])
Create an unsigned/signed integer assigned with ‘value’ UInt
SInt
U”[[size’]base]value”
S”[[size’]base]value”
Create an unsigned/signed integer assigned with ‘value’ (Base : ‘h’, ‘d’, ‘o’, ‘b’) UInt
SInt
U([x bits,] element, …)
S([x bits,] element, …)
Create an unsigned integer assigned with the value specified by elements UInt
SInt
val myUInt = UInt(8 bits)
myUInt := U(2,8 bits)
myUInt := U(2)
myUInt := U"0000_0101"  // Base per default is binary => 5
myUInt := U"h1A"        // Base could be x (base 16)
                        //               h (base 16)
                        //               d (base 10)
                        //               o (base 8)
                        //               b (base 2)                       
myUInt := U"8'h1A"       
myUInt := 2             // You can use scala Int as literal value

val myBool := myUInt === U(7 -> true,(6 downto 0) -> false)
val myBool := myUInt === U(myUInt.range -> true)

// For assignement purposes, you can omit the U/S, which also alow the use of the [default -> ???] feature
myUInt := (default -> true)                        //Assign myUInt with "11111111"
myUInt := (myUInt.range -> true)                   //Assign myUInt with "11111111"
myUInt := (7 -> true, default -> false)            //Assign myUInt with "10000000"
myUInt := ((4 downto 1) -> true, default -> false) //Assign myUInt with "00011110"

Operators

The following operators are available for the UInt and SInt type

Logic

Operator Description Return type
x ^ y Logical XOR Bool
~x Bitwise NOT T(w(x) bits)
x & y Bitwise AND T(max(w(xy) bits)
x | y Bitwise OR T(max(w(xy) bits)
x ^ y Bitwise XOR T(max(w(xy) bits)
x.xorR XOR all bits of x Bool
x.orR OR all bits of x Bool
x.andR AND all bits of x Bool
x >> y Arithmetic shift right, y : Int T(w(x) - y bits)
x >> y Arithmetic shift right, y : UInt T(w(x) bits)
x << y Arithmetic shift left, y : Int T(w(x) + y bits)
x << y Arithmetic shift left, y : UInt T(w(x) + max(y) bits)
x |>> y Logical shift right, y : Int/UInt T(w(x) bits)
x |<< y Logical shift left, y : Int/UInt T(w(x) bits)
x.rotateLeft(y) Logical left rotation, y : UInt/Int T(w(x) bits)
x.rotateRight(y) Logical right rotation, y : UInt/Int T(w(x) bits)
x.clearAll[()] Clear all bits -
x.setAll[()] Set all bits -
x.setAllTo(value : Boolean) Set all bits to the given Boolean value -
x.setAllTo(value : Bool) Set all bits to the given Bool value -
// Bitwise operator
val a, b, c = SInt(32 bits)
c := ~(a & b) //  Inverse(a AND b)

val all_1 = a.andR // Check that all bit are equal to 1

// Logical shift
val uint_10bits = uint_8bits << 2  // shift left (result on 10 bits)
val shift_8bits = uint_8bits |<< 2 // shift left (result on 8 bits)

// Logical rotation
val myBits = uint_8bits.rotateLeft(3) // left bit rotation

// Set/clear
val a = B"8'x42"
when(cond){
  a.setAll() // set all bits to True when cond is True
}

Arithmetic

Operator Description Return
x + y Addition T(max(w(x), w(y) bits)
x - y Subtraction T(max(w(x), w(y) bits)
x * y Multiplication T(w(x) + w(y) bits)
x / y Division T(w(x) bits)
x % y Modulo T(w(x) bits)
// Addition
val res = mySInt_1 + mySInt_2

Comparison

Operator Description Return type
x === y Equality Bool
x =/= y Inequality Bool
x > y Greater than Bool
x >= y Greater than or equal Bool
x > y Less than Bool
x >= y Less than or equal Bool
// Comparaison between two SInt
myBool := mySInt_1 > mySInt_2

// Comparaison between UInt and a literal
myBool := myUInt_8bits >= U(3, 8 bits)

when(myUInt_8bits === 3){

}

Type cast

Operator Description Return
x.asBits Binary cast in Bits Bits(w(x) bits)
x.asUInt Binary cast in UInt UInt(w(x) bits)
x.asSInt Binary cast in SInt SInt(w(x) bits)
x.asBools Cast into a array of Bool Vec(Bool, w(x))
S(x: T) Cast a Data into a SInt SInt(w(x) bits)
U(x: T) Cast a Data into an UInt UInt(w(x) bits)

To cast a Bool, a Bits or a SInt into a UInt, you can use U(something). To cast things into a SInt, you can use S(something)

// cast a SInt to Bits
val myBits = mySInt.asBits

// create a Vector of bool
val myVec = myUInt.asBools

// Cast a Bits to SInt
val mySInt = S(myBits)

Bit extraction

Operator Description Return
x(y) Readbit, y : Int/UInt Bool
x(offset, width) Read bitfield, offset: UInt, width: Int T(width bits)
x(range) Read a range of bit. Ex : myBits(4 downto 2) T(range bits)
x(y) := z Assign bits, y : Int/UInt Bool
x(offset, width) := z Assign bitfield, offset: UInt, width: Int T(width bits)
x(range) := z Assign a range of bit. Ex : myBits(4 downto 2) := U”010” T(range bits)
// get the element at the index 4
val myBool = myUInt(4)

// assign
mySInt(1) := True

// Range
val myUInt_8bits = myUInt_16bits(7 downto 0)
val myUInt_7bits = myUInt_16bits(0 to 6)
val myUInt_6bits = myUInt_16Bits(0 until 6)

mySInt_8bits(3 downto 0) := mySInt_4bits

Misc

Operator Description Return
x.getWidth Return bitcount Int
x.msb Return the most significant bit Bool
x.lsb Return the least significant bit Bool
x.range Return the range (x.high downto 0) Range
x.high Return the upper bound of the type x Int
x ## y Concatenate, x->high, y->low Bits(w(x) + w(y) bits)
x @@ y Concatenate x:T with y:Bool/SInt/UInt T(w(x) + w(y) bits)
x.subdivideIn(y slices) Subdivide x in y slices, y: Int Vec(T, y)
x.subdivideIn(y bits) Subdivide x in multiple slices of y bits, y: Int Vec(T, w(x)/y)
x.resize(y) Return a resized copy of x, if enlarged, it is filled with zero
for UInt or filled with the sign for SInt, y: Int
T(y bits)
x.resized Return a version of x which is allowed to be automatically
resized were needed
T(w(x) bits)
myUInt.twoComplement(en: Bool) Use the two’s complement to transform an UInt into an SInt SInt(w(myUInt) + 1)
mySInt.abs Return the absolute value of the SInt value SInt(w(mySInt))
mySInt.abs(en: Bool) Return the absolute value of the SInt value when en is True SInt(w(mySInt))
myBool := mySInt.lsb  // equivalent to mySInt(0)

// Concatenation
val mySInt = mySInt_1 @@ mySInt_1 @@ myBool   
val myBits = mySInt_1 ## mySInt_1 ## myBool   

// Subdivide
val sel = UInt(2 bits)
val mySIntWord = mySInt_128bits.subdivideIn(32 bits)(sel)
    // sel = 0 => mySIntWord = mySInt_128bits(127 downto 96)
    // sel = 1 => mySIntWord = mySInt_128bits( 95 downto 64)
    // sel = 2 => mySIntWord = mySInt_128bits( 63 downto 32)
    // sel = 3 => mySIntWord = mySInt_128bits( 31 downto  0)

 // if you want to access in a reverse order you can do
 val myVector   = mySInt_128bits.subdivideIn(32 bits).reverse
 val mySIntWord = myVector(sel)

// Resize
myUInt_32bits := U"32'x112233344"
myUInt_8bits  := myUInt_32bits.resized       // automatic resize (myUInt_8bits = 0x44)
myUInt_8bits  := myUInt_32bits.resize(8)     // resize to 8 bits (myUInt_8bits = 0x44)

// Two's complement
mySInt := myUInt.twoComplement(myBool)

// Absolute value
mySInt_abs := mySInt.abs
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