staydigital circuit The shift register is a kind oftriggerBased device, data is input into the device in parallel or serial mode, and each time pulse moves one to the left or right in turnBit, output at the output end.This shift register is one-dimensional. In fact, there are multi-dimensional shift registers, that is, the input and output data are columns.The way to realize this multidimensional shift register can be to parallel several shift registers with the same number of bits.
displacementregisterThe data in can be shiftedpulseThe data can be input and output in parallel, serial input and output, parallel input and output, serial input and output, serial input and output, serial input and parallel output. It is very flexible and widely used.
principle
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The shift register can not only store data, but also shift the data left or right in turn under the action of the clock signal.
The schematic diagram of the four bit shift register is shown in Figure 1.FF0, FF1, FF2 and FF3 are D flip-flop triggered by four edges. The output terminal Q of each flip-flop is connected to the input terminal D of one flip-flop on the right.Because there is a delay time from the time when the rising edge of the clock signal CP is added to the trigger to the time when the new state of the output terminal is stably established, when the clock signal is added to four triggers at the same time, each trigger receives the original data in the left trigger (input data D1 received by FF0).The data in the register is shifted one bit to the right in turn.
Figure 1 Four bit shift register
characteristic
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displacementregisterIt can be used to store code, realize serial parallel data conversion, numerical operation and data processing.
Integrated circuit
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Common integrated shiftsregisterThere are many types, such as 74X164, 74X165, 74X166, 74X595, 74195, 74194, 74194, 74198 and 74198, which are all eight bit one-way shift registers, four bit one-way shift registers, four bit bidirectional shift registers, and eight bit bidirectional shift registers.
Figure 2 74LS674
classification
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According to the shift direction, it is often divided into left shift register, right shift register and bidirectional shift register;
According to the input output mode of shift data, it can be divided into four circuit structures: serial input serial output, serial input parallel output, parallel input serial output and parallel input parallel output.
In addition, some shift registers also have the function of preset number, which can put data into the register in parallel.
The shift register can be used for data operation, data processing, serial parallel data conversion, and can also be connected to various shift register counters, such as ring countersJohnson counter Etc.
