Programming method and application of single chip microcomputer serial interface

Communication between the MCU and the PC. For example, the data collected by the MCU measurement and control system is sent to the host computer through the RS-232 interface. As shown in Figures 1 and 2. Usually, auxiliary software is required, such as Figure 3 serial port debugging assistant and Figure 4 host computer communication software.

Figure 1 MCU serial port connection

Figure 2 Communication between MCU and PC

Figure 3 Serial port debugging assistant

Figure 4 Host computer communication software

Example 1: Use serial port working mode 0 to expand an 8-bit parallel I/O port, where 74LS164 is a serial-input-parallel-output chip that drives the common-anode LED digital tube to display 0~9.

Answer: The basic principle of expansion is shown in Figure 5

Figure 5: Serial port mode 0 expansion

 

The encoding principle is shown in Figure 6.

Figure 6 LED coding principle diagram

The subroutine to display the numbers 0-9 is shown below.

DSPLY:MOV   DPTR, #TABLE

      MOVC A, @A+DPTR

      MOV SBUF, A

      JNB TI, $

      CLR IT

      RIGHT

TABLE:DB 0C0H,0F9H,0A4H,0B0H,99H,92H,82H,0F8H,80H,90H;Digital codes from 0 to 9

Example 2: Dual-machine communication. As shown in Figure 7, connect two CS-III microcontroller experiment boards, set the baud rate to 9600, connect the TXD and RXD ports of the transmitter and receiver, connect the TXD port of the transmitter to the RXD port of the receiver, and the RXD port of the receiver to the TXD port of the transmitter, and connect the ground terminals of the two machines.

Figure 7 Schematic diagram of two-machine communication

Answer: Serial communication applications generally require the correct setting of the serial port working mode, calculation of the baud rate, initialization of the baud rate setting and serial port initialization, as well as related register settings. The serial communication flow chart is shown in Figure 8.

Figure 8 Two-machine communication flow chart