Interface circuit composed of 74LS164 and 8051 microcontroller

The interface circuit of 74LS164 and 8051 microcontroller is shown in the figure below. When the serial port of the 51 series microcontroller works in the sending state of mode 0, the serial data is sent out by P3.0 (RXD) and the shift clock is sent out by P3.1 (TXD). Under the action of the shift clock, the data in the serial port send buffer is shifted into 74LS164 bit by bit.

If the serial port is occupied by other devices, you can use the ordinary I/O port to simulate the timing of the shift register to send data to the 74LS164. Practice has proved that this is a convenient, economical and feasible method. P1.5 is used to output serial data, and P1.6 is used for shift clock output.

In practical applications, it should also be noted that 74LS164 does not have a parallel output control terminal. When serial data is input, the parallel output port will change continuously. If necessary, an output tri-state gate control can be added to the output terminal of 74LS164 to ensure that the output is output after the serial input is completed.