Shift Arithmetic
R2026bShift bits or binary point of signal
Shift Arithmetic block
To add a block to a model, double-click the canvas and start typing the block name. Then, select the block from the list.
Libraries:
Simulink /
Logic and Bit Operations
HDL Coder /
Logic and Bit Operations
Description
The Shift Arithmetic block can shift the bits or the binary point of an input signal, or both.
For example, shifting the binary point on an input of data type sfix(8)
by two places to the right and left gives these decimal values.
| Shift Operation | Binary Value | Decimal Value |
|---|---|---|
No shift (original number) | 11001.011 | –6.625 |
Binary point shift right by two places | 1100101.1 | –26.5 |
Binary point shift left by two places | 110.01011 | –1.65625 |
This block performs arithmetic bit shifts on signed numbers. Therefore, the block recycles
the most significant bit for each bit shift. Shifting the bits on an input of data type
sfix(8) by two places to the right and left gives these decimal
values.
| Shift Operation | Binary Value | Decimal Value |
|---|---|---|
No shift (original number) | 11001.011 | –6.625 |
Bit shift right by two places | 11110.010 | –1.75 |
Bit shift left by two places | 00101.100 | 5.5 |
To shift in either direction, set the direction to
Bidirectional.
Examples
This example shows the effect of binary point shifts.
model='ex_shift_arithmetic_block_binary_point_shifts';
open_system(model)
This example shows a comparison of the behavior of right bit shifts using the dialog box versus the block input port.
model='ex_shift_arithmetic_block_right_bit_shifts';
open_system(model)
Ports
Input
Output
Parameters
Block Characteristics
Data Types |
|
Direct Feedthrough |
|
Multidimensional Signals |
|
Variable-Size Signals |
|
Zero-Crossing Detection |
|
Programmatic Use: Add Block
To add the block programmatically, use the add_block function with one of these library block paths as the source.
"simulink/Logic and Bit Operations/Shift Arithmetic"
"hdlsllib/Logic and Bit Operations/Shift Arithmetic"
Example: add_block("simulink/Logic and Bit Operations/Shift Arithmetic","myModel/myBlock",MakeNameUnique="on")
More About
The Behavior of Right Bit Shifts example compares the behavior of right bit shifts using the dialog box versus the block input port.
The key block parameter settings of the Constant blocks are:
| Block | Parameter | Setting |
|---|---|---|
Constant and Constant1
| Constant value |
124
|
| Output data type |
int8
| |
Dynamic bit shift
| Constant value |
2
|
| Output data type |
Inherit: Inherit from 'Constant value'
|
The key block parameter settings of the Shift Arithmetic blocks are:
| Block | Parameter | Setting |
|---|---|---|
Bit shift from dialog
| Bits to shift: Source |
Dialog
|
| Bits to shift: Direction |
Right
| |
| Bits to shift: Number |
2
| |
Bit shift from input
| Bits to shift: Source |
Input port
|
| Bits to shift: Direction |
Right
|
The top Shift Arithmetic block takes an input of 124, which corresponds to 01111100 in binary format. Shifting the number of bits two places to the right produces 00011111 in binary format. Therefore, the block outputs 31.
The bottom Shift Arithmetic block performs the same operation as the top block. However, the bottom block receives the bit shift value through an input port instead of the dialog box. By supplying this value as an input signal, you can change the number of bits to shift during simulation.
The Effect of Binary Point Shifts example shows the effect of binary point shifts.
The key block parameter settings of the Constant blocks are:
| Block | Parameter | Setting |
|---|---|---|
Constant and Constant1
| Constant value |
124
|
| Output data type |
int8
|
The key block parameter settings of the Shift Arithmetic blocks are:
| Block | Parameter | Setting |
|---|---|---|
Shift binary point 3 places to the right
| Bits to shift: Source |
Dialog
|
| Bits to shift: Direction |
Bidirectional
| |
| Bits to shift: Number |
0
| |
| Binary points to shift: Number |
3
| |
Shift binary point 3 places to the left
| Bits to shift: Source |
Dialog
|
| Bits to shift: Direction |
Bidirectional
| |
| Bits to shift: Number |
0
| |
| Binary points to shift: Number | – 3
|
The top Shift Arithmetic block takes an input of 124, which corresponds to 01111100 in binary format. Shifting the binary point three places to the right produces 01111100000 in binary format. Therefore, the top block outputs 995.
The bottom Shift Arithmetic block also takes an input of 124. Shifting the binary point three places to the left produces 01111.100 in binary format. Therefore, the bottom block outputs 15.5.
Algorithms
Suppose that WL is the input word length. The shaded regions in
the following diagram show out-of-range bit shift values for left and right
shifts.
Similarly, the shaded regions in the following diagram show out-of-range bit shift values for bidirectional shifts.
The diagnostic for out-of-range bit shifts responds as follows, depending on the mode of operation:
| Mode | Diagnostic for out-of-range shift value | ||
|---|---|---|---|
| None | Warning | Error | |
| Simulation modes | Do not report any warning or error. | Report a warning but continue simulation. | Report an error and stop simulation. |
| Code generation | Has no effect. | ||
Suppose that U is the input, WL is the input
word length, and Y is the output. The output for an out-of-range
bit shift value for left shifts is as follows:
Similarly, the output for an out-of-range bit shift value for right shifts is as follows:
For bidirectional shifts, the output for an out-of-range bit shift value is as follows:
Extended Capabilities
Version History
Introduced before R2006a
