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The IC also generates the requisite control signals. This is essentially a programmed PIC controller that produces a Centronics compatible signal from a 2400 baud serial signal (eight data bits, no parity, one stop bit).
The serial-to-parallel conversion is effected by IC1. This is an integrated level converter that transforms the single +5V supply into a symmetrical ☑2V one. Since the computer needs real RS232 levels, an adaptation from TTL to RS232 is provided in the converter by a MAX232. The CTS and DSR signals enable handshaking to be implemented. The TxD line, pin 3, CTS line, pin 8 and the DSR line, pin 6, of the serial port are used – see diagram. It converts a serial 2400 baud signal into a parallel signal. Similarly, the N-bit PIPO shift register doesn’t require any clock pulse in order to shift ‘N’ bit information.This converter may help if just the serial port on a personal computer is free, whereas the printer needs a parallel (Centronics) port. Therefore, the 3-bit PIPO shift register requires zero clock pulses in order to produce the valid output. So, the binary information “011” is obtained in parallel at the outputs of D flip-flops before applying positive edge of clock. Let us see the working of 3-bit SISO shift register by sending the binary information “011” from LSB to MSB serially at the input.Īssume, initial status of the D flip-flops from leftmost to rightmost is $Q_=011$. Hence, this output is also called as serial output. So, we can receive the bits serially from the output of right most D flip-flop. For every positive edge triggering of clock signal, the data shifts from one stage to the next. Hence, this input is also called as serial input. In this shift register, we can send the bits serially from the input of left most D flip-flop. All these flip-flops are synchronous with each other since, the same clock signal is applied to each one. That means, output of one D flip-flop is connected as the input of next D flip-flop. This block diagram consists of three D flip-flops, which are cascaded. The block diagram of 3-bit SISO shift register is shown in the following figure. The shift register, which allows serial input and produces serial output is known as Serial In – Serial Out (SISO) shift register. Serial In − Serial Out (SISO) Shift Register Parallel In − Parallel Out shift register.Parallel In − Serial Out shift register.Serial In − Parallel Out shift register.Following are the four types of shift registers based on applying inputs and accessing of outputs. An ‘N’ bit shift register contains ‘N’ flip-flops. If the register is capable of shifting bits either towards right hand side or towards left hand side is known as shift register. The group of flip-flops, which are used to hold (store) the binary data is known as register. In order to store multiple bits of information, we require multiple flip-flops. We know that one flip-flop can store one-bit of information.