Combinatorial Logic shifter. Barrel Shifter.

Ports

Port Name	Type	Usage	Description	Comments
Data	I	Required	Data to be shifted.	Vector, LPM_Width wide
Distance	I	Required	Number of positions to shift Data.	Vector, LPM_WidthDist wide
Direction	I	Optional	Direction of shift. Low = Left (toward MSB) High = Right (toward LSB)	Default value is 0 (Low) = Left (toward the MSB)
Result	O	Required	Shifted Data	Vector, LPM_Width wide
Overflow	O	Optional	Logical or Arithmetic Overflow	Note 1
Underflow	O	Optional	Logical or Arithmetic Underflow	Note 1

Note 1: If the LPM_ShiftType is ROTATE and Overflow or Underflow are connected, the output of those ports will be undefined.

Properties

Property	Usage	Value	Comments
LPM_Width	Required	LPM Value > 0	Width of input vector
LPM_WidthDist	Optional	LPM Value > 0	Width of the Distance Port Note 1
LPM_ShiftType	Optional	LOGICAL | ROTATE | ARITHMETIC	Default is LOGICAL Note 2

Note 1: LPM_WidthDist specifies the width of the Distance port. The values on the Distance port would normally range from 0 which would mean "no shift" to (LPM_Width-1) which would be the maximum meaningful shift. The typical value assigned to LPM_WidthDist would be "the smallest integer not less than log₂(LPM_Width)" or log₂LPM_Width. Any value on the Distance port greater than LPM_Width-1 results in an UNDEFINED output.

Note 2: The sign bit is extended for ARITHMETIC. For a LOGICAL right shift 0's are always shifted into the MSB.

Functions
The LPM_CLSHIFT module acts like a barrel-shifter. It is entirely combinational logic.

Overflow occurs when the shifted result exceeds the precision of the Result bus. For LOGICAL values, overflow occurs when all ones have been shifted out. For ARITHMETIC value, overflow occurs a significant digit is shifted into or past the sign bit.

Underflow occurs when the shifted result contains no significant digits.

LPM_ShiftType	Direction	Function
LOGICAL	0 = Left	Result = Data << Distance
LOGICAL	1 = Right	Result = Data >> Distance
ROTATE	0 = Left	Resulti = Datax where x is ((Distance + i ) mod LPM_Width)
ROTATE	1 = Right	Resulti = Datax where x is ((Distance - i ) mod LPM_Width)
ARITHMETIC	0 = Left	Result = DATA * 2LPM_Distance
ARITHMETIC	1 = Right	Result = DATA 2LPM_Distance (integer divide)

Values larger than (LPM_Width - 1) result in an UNDEFINED output.