SIMPLIS Parts
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The Barrel Shifter with both Async and Sync Set/Reset models a combination of a clocked data type register and a barrel shifter. The barrel shifter is similar to the multi-bit shift register, except that bits shifted of the register are shifted back into the opposite end of the register. For example, in right shift operations, the LSBs shifted out of the register are shifted into the MSBs. The clock edge for the register can be set with the Trigger Condition parameter to be a rising edge (0_TO_1) or a falling edge (1_TO_0). Both asynchronous and synchronous set and reset inputs are provided. The active logic level of the inputs can be configured with the Set/Reset Level and Load/Shift Level parameters.
For the barrel shifter with either asynchronous or synchronous set and reset inputs, see Barrel Shifter.
Related topics:
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Model Name: |
Barrel Shifter with both Async and Sync Set/Reset |
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Simulator: |
This device is compatible with the SIMPLIS simulator. |
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Parts Selector |
Digital Functions | Registers |
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Symbol Library: |
None - the symbol is automatically generated when placed or edited. |
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Model File: |
None - the device model is generated before simulation. |
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Subcircuit Name: |
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Symbol: |
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Multiple Selections: |
Only one device at a time can be edited. |
To configure the barrel shifter with both async and sync set/reset, follow these steps:
Label | Parameter Description |
Clock to Output Delay |
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Number of Bits |
Number of input and output bits for the barrel shifter |
Trigger Condition |
Determines the triggering condition of the barrel shifter clock pin:
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Ground Ref |
Determines whether or not a device has a ground reference pin. |
Minimum Clock Width |
Minimum valid clock width. Clock widths less than this parameter will not trigger the barrel shifter. |
Setup Time |
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Hold Time |
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Initial Condition |
Initial condition of the barrel shifter output in decimal |
Left/Right Level |
Determines the logic level of the barrel shifter left/right (L/R) pin:
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Load/Shift Level |
Determines the logic level of the barrel shifter load/shift (LD/SH) pin:
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To define the set/reset behavior of the barrel shifter, follow these steps from the Barrel Shifter with both Async and Sync Set/Reset dialog box:
Label | Parameter Description |
Set/Reset Level |
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Asynchronous Set/Reset Parameters |
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Set To |
Determines the barrel shifter output value when the asynchronous set pin goes active |
Reset To |
Determines the barrel shifter output value when the asynchronous reset pin goes active |
Set/Reset Delay |
Delay from when the set or reset pin goes active until the output is actually set or reset |
Synchronous Set/Reset Parameters |
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Set To |
Determines the barrel shifter output value when the synchronous set pin goes active |
Reset To |
Determines the barrel shifter output value when the synchronous reset pin goes active |
To define the parameters for the interface between this digital component and each analog component connected directly to an input or output pin, follow these steps from the Barrel Shifter with both Async and Sync Set/Reset dialog box:
Label | Parameter Description | |||||||
Input Resistance |
Input resistance of each input pin |
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Threshold Hysteresis |
The Threshold (T) and Hysteresis (H) of the Schmitt trigger input buffer on each Barrel Shifter input. To determine the low-to-high threshold (TH) and the high-to-low threshold (TL), substitute Threshold (T) and Hysteresis (H) in each of the following formulas :
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Output Resistance |
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Output High Voltage |
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Output Low Voltage |
The following truth table assumes these parameter values:
When the EN input is high and the Load/Shift Level=Load_1/Shift_0, the register will load the D input when the LD/SH pin is high and shift the Q output when the LD/SH pin is low.
Inputs |
Output |
Action |
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LD/SH |
SET |
RST |
ASET |
ARST |
EN |
L/R |
CLK |
Q |
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0 |
0 |
0 |
0 |
0 |
Last Q |
Retain state |
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1 |
0 |
0 |
0 |
0 |
1 |
Data input |
Load data |
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0 |
0 |
0 |
0 |
0 |
1 |
0 |
Q = Last Q shifted left SC bits. |
Shift left |
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0 |
0 |
0 |
0 |
0 |
1 |
1 |
Q = Last Q shifted right SC bits. |
Shift Right |
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1 |
0 |
0 |
0 |
Synchronous Set To value |
Synchronous set |
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0 |
1 |
0 |
0 |
Synchronous Reset To value |
Synchronous reset |
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1 |
0 |
Asynchronous Set To value |
Asynchronous set |
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0 |
1 |
Asynchronous Reset To value |
Asynchronous reset |
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1 |
1 |
0 |
0 |
Last Q |
Illegal concurrent SET and RST |
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1 |
1 |
Last Q |
Illegal concurrent ASET and ARST |
The test circuit used to generate the waveform examples in the next section can be downloaded here: simplis_049_barrelshifters_example.zip.
To simulate this design, follow these steps:
This example of the barrel shifter with both async and sync set/reset uses two Digital Signal Sources to generate the input pulses to the barrel shifter with both async and sync set/reset. The input source waveforms are defined in a text file with each state transition defined on a single line. These two sources excite every state transition in the truth table.
For clarity, the simulation waveforms taken from the circuit example have been divided into two sections.
The image below shows the load and shift behavior of the barrel shifter. The initial condition of the barrel shifter with both async and sync set/reset is set to 255 decimal in the example.
Time | Event | Q Output (binary) |
100n |
Load | 0000 0101 |
200n |
Retain state | 0000 0101 |
300n |
Shift left 4 places | 0101 0000 |
400n |
Shift right 2 places | 0001 0100 |
500n |
Shift right 2 places | 0000 0101 |
600n |
Shift left 6 places | 0100 0001 |
700n |
Shift right 2 places | 0101 0000 |
800n |
Shift right 4 places | 0000 0101 |
The image below shows the asynchronousa nd synchronous set/reset behavior of the barrel shifter.
Time | Event | Q Output |
1.1u |
Synchronous set | 156 |
1.2u |
Synchronous reset | 2 |
1.3u |
Load | 5 |
1.4u |
Illegal concurrent SET and RST | 5 |
1.52u |
Asynchronous set | 200 |
1.62u |
Asynchronous reset | 1 |
1.7u |
Load | 5 |
1.82u |
Illegal concurrent ASET and ARST | 5 |
Because the barrel shifter with both async and sync set/reset model is generated by a template script when the simulation is executed, a fixed model cannot be inserted into a netlist. The template script for this device is simplis_make_register_model.sxscr, which you, as a licensed user, can download in a zip archive of all built-in scripts.
To download this zip file, follow these steps:
Note: You will be prompted to log in with the user name and password given to you when you registered.