Bitwise Operator - Specified bitwise operation on inputs

Library

Logic and Bit Operations

Description

Bitwise Operations

The Bitwise Operator block performs the bitwise operation that you specify on one or more operands. Unlike logic operations of the Logical Operator block, bitwise operations treat the operands as a vector of bits rather than a single value.

You can select one of the following bitwise operations:

Bitwise Operation	Description
AND	TRUE if the corresponding bits are all TRUE
OR	TRUE if at least one of the corresponding bits is TRUE
NAND	TRUE if at least one of the corresponding bits is FALSE
NOR	TRUE if no corresponding bits are TRUE
XOR	TRUE if an odd number of corresponding bits are TRUE
NOT	TRUE if the input is FALSE (available only for single input)

Restrictions on Block Operations

The Bitwise Operator block does not support shift operations. For shift operations, use the Shift Arithmetic block.

When configured as a multi-input XOR gate, this block performs modulo-2 addition according to the IEEE^® Standard for Logic Elements.

Behavior of Inputs and Outputs

The output data type, which the block inherits from the driving block, must represent zero exactly. Data types that satisfy this condition include signed and unsigned integer data types.

The size of the block output depends on the number of inputs, the vector size, and the operator you select:

• The NOT operator accepts only one input, which can be a scalar or a vector. If the input is a vector, the output is a vector of the same size containing the bitwise logical complements of the input vector elements.

• For a single vector input, the block applies the operation (except the NOT operator) to all elements of the vector.

  • If you do not specify a bit mask, the output is a scalar.

  • If you do specify a bit mask, the output is a vector.

• For two or more inputs, the block performs the operation between all of the inputs. If the inputs are vectors, the block performs the operation between corresponding elements of the vectors to produce a vector output.

Bit Mask Behavior

Block behavior changes depending on whether you use a bit mask.

If the Use bit mask check box is...	The block accepts...	And you specify...	By using...
Selected	One input	Bit Mask	Any valid MATLAB expression, such as 2^5+2^2+2^0 for the bit mask 00100101
Not selected	Multiple inputs, all having the same base data type	Number of input ports	Any positive integer greater than 1

Tip   You can also use strings to specify a hexadecimal bit mask such as {'FE73','12AC'}.

Bit Set and Bit Clear Operations

You can use the bit mask to set or clear a bit on the input.

To perform a...	Set the Operator parameter to...	And create a bit mask with...
Bit set	OR	A 1 for each corresponding input bit that you want to set to 1
Bit clear	AND	A 0 for each corresponding input bit that you want to set to 0

Suppose you want to set the fourth bit of an 8-bit input vector. The bit mask would be 00010000, which you can specify as 2^4 for the Bit Mask parameter. To clear the bit, the bit mask would be 11101111, which you can specify as 2^7+2^6+2^5+2^3+2^2+2^1+2^0 for the Bit Mask parameter.

Data Type Support

The Bitwise Operator block supports the following data types:

• Built-in integer

• Fixed point

• Boolean

The block does not support floating-point data types or enumerated data types. For more information, see Data Types Supported by Simulink in the Simulink documentation.

Parameters and Dialog Box

Operator

Specify the bitwise logical operator for the block operands.

Use bit mask

Select to use the bit mask. Clearing this check box enables Number of input ports and disables Bit Mask and Treat mask as.

Number of input ports

Specify the number of inputs. The default value is 1.

Bit Mask

Specify the bit mask to associate with a single input. This parameter is available only when you select Use bit mask.

Tip   Do not use a mask greater than 53 bits. Otherwise, an error message appears during simulation.

Treat mask as

Specify whether to treat the mask as a real-world value or a stored integer. This parameter is available only when you select Use bit mask.

The encoding scheme is V = SQ + B, as described in Scaling in the Simulink Fixed Point documentation. Real World Value treats the mask as V. Stored Integer treats the mask as Q.

Examples

Unsigned Inputs for the Bitwise Operator Block

The following model shows how the Bitwise Operator block works for unsigned inputs.

Each Constant block outputs an 8-bit unsigned integer (uint8). To determine the binary value of each Constant block output, use the dec2bin function. The results for all logic operations appear in the next table.

Operation	Binary Value	Decimal Value
AND	00101000	40
OR	11111101	253
NAND	11010111	215
NOR	00000010	2
XOR	11111000	248
NOT	N/A	N/A

Signed Inputs for the Bitwise Operator Block

The following model shows how the Bitwise Operator block works for signed inputs.

Each Constant block outputs an 8-bit signed integer (int8). To determine the binary value of each Constant block output, use the dec2bin function. The results for all logic operations appear in the next table.

Operation	Binary Value	Decimal Value
AND	01000000	64
OR	11111011	–5
NAND	10111111	–65
NOR	00000100	4
XOR	11000010	–62
NOT	N/A	N/A

Characteristics

Direct Feedthrough	Yes
Sample Time	Inherited from the driving block
Scalar Expansion	Yes, of inputs
Multidimensionalized	Yes
Zero-Crossing Detection	No

See Also

Logical Operator

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