Parallel In Serial Out Shift Register Truth Table
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How to Use a Parallel In Serial Out Shift Register
A parallel in serial out (PISO) shift register is a type of digital circuit that can store multiple bits of data in parallel and output them serially. A PISO shift register consists of a series of flip-flops connected in a chain, with each flip-flop storing one bit of data. The data can be loaded into the shift register in parallel, meaning that all the bits are entered at the same time. The data can then be shifted out of the shift register serially, meaning that one bit is output at a time.
A PISO shift register can be useful for applications that require converting parallel data to serial data, such as transmitting data over a single wire or displaying data on a serial LED display. To use a PISO shift register, you need to understand how it works and how to control it with logic signals.
How a PISO Shift Register Works
A PISO shift register has three main inputs: parallel load (PL), clock (CLK), and serial input (SI). It also has one main output: serial output (SO). The PL input determines whether the data is loaded in parallel or shifted out serially. The CLK input controls the timing of the data movement. The SI input allows new data to be entered serially while shifting out the existing data. The SO output provides the serial data stream.
The basic operation of a PISO shift register is as follows:
When PL is high, the data on the parallel inputs (P0, P1, ..., Pn) is loaded into the flip-flops simultaneously. The SO output reflects the state of the last flip-flop.
When PL is low, the data in the flip-flops is shifted to the right by one position on each rising edge of CLK. The SO output reflects the state of the last flip-flop. The SI input provides the new data for the first flip-flop.
The following diagram shows an example of a 4-bit PISO shift register with its truth table:
How to Control a PISO Shift Register with Logic Signals
To control a PISO shift register with logic signals, you need to provide the appropriate values for the PL, CLK, and SI inputs. You can use switches, buttons, or other devices to generate these signals manually, or you can use a microcontroller or a computer to generate them programmatically.
The following steps describe how to control a PISO shift register with logic signals:
Set the PL input to high and provide the parallel data on the P0, P1, ..., Pn inputs. The data will be loaded into the flip-flops and the SO output will show the last bit.
Set the PL input to low and provide the clock pulses on the CLK input. The data will be shifted out of the flip-flops one bit at a time and the SO output will show the serial data stream. The SI input can be used to enter new data serially while shifting out the existing data.
Repeat steps 1 and 2 as needed to load and shift out different data.
How to Use a PISO Shift Register in a Circuit
A PISO shift register can be used in a circuit to perform various functions, such as converting parallel data to serial data, expanding the number of inputs or outputs of a microcontroller, or interfacing with serial devices. To use a PISO shift register in a circuit, you need to connect it to the appropriate power supply, ground, and logic signals. You also need to connect it to the devices that provide or receive the data.
The following diagram shows an example of a circuit that uses a PISO shift register to convert parallel data from four switches to serial data for an LED display:
In this circuit, the four switches are connected to the parallel inputs of the shift register. The PL input is connected to a push button that loads the switch states into the flip-flops when pressed. The CLK input is connected to a 555 timer that generates clock pulses at a fixed frequency. The SI input is connected to ground, meaning that no new data is entered serially. The SO output is connected to an LED display that shows the serial data stream.
When the push button is pressed, the switch states are loaded into the flip-flops and the LED display shows the last bit. When the push button is released, the switch states are shifted out of the flip-flops one bit at a time and the LED display shows the serial data stream. The 555 timer controls the speed of the shifting process. aa16f39245