The $GPGGA information of GPS is read by PIC 16f877 single chip microcomputer and displayed by YJD 1602 liquid crystal.

In recent years, due to the rapid development of semiconductor technology, the manufacturing cost of electronic products has been greatly reduced, and the use of electronic products has gradually become an indispensable part of people's daily life. Due to the different needs of users, electronic products also need constant innovation and change. At present, many electronic products need to use single chip microcomputer as the control core. The characteristic of this kind of products is that as long as the written control program is written into the memory of the single chip microcomputer and some peripheral electronic components are connected to the single chip microcomputer, a new electronic product can be formed, and this kind of electronic products can be seen everywhere in daily life. For example, the music ic on the birthday card, various remote controllers, mobile phones, home appliances, cars and other products all have the use of single chip microcomputer. In addition, in personal computers (PC) and related peripherals, single-chip computers are also needed. In addition, in industrial control applications, single-chip computers are also indispensable.

After studying and using the Intel MCS-5 1 series single-chip microcomputer, we decided to study the Microchip PIC 16F87X series single-chip microcomputer, taking PIC 16F877 as the research goal, and discussed the composition, program development and control application technology of single-chip microcomputer, and then extended it to the application and application circuit design of other types of single-chip microcomputer.

Wojiansuke

1. 1 basic structure of single chip microcomputer

Single chip microcomputer consists of three parts: central processing unit (CPU), storage unit and input/output unit. CPU can be divided into two parts, namely arithmetic logic (ALU) and control unit (CU). The CPU performs reading, decoding, arithmetic logic operation and control of reading and writing timing signals through the bus. Storage units provide space for storing programs and data, including read-only memory (ROM) and random access memory (RAM). And the input/output unit provides a conduit for communication with external peripheral devices or components.

1. 1. 1 single chip microcomputer

Single-chip microcomputer is referred to as single-chip microcomputer for short. The so-called single-chip microcomputer is to make the central processing unit (CPU), storage unit, input/output (I/O), clock generation unit and related peripheral devices into a microcomputer system, and make them on the same chip to become a control system that can run independently.

1.2 PIC 16F877 single chip microcomputer

PIC 16F87X series single chip microcomputer is a product of Microchip company. It is an eight-bit microcomputer-controlled single chip microcomputer of RISC, equipped with up to 8K Flah program memory, five groups of I/O ports, and supports up to 14 interrupts.

The characteristics of PIC 16F877 are described as follows:

● Adopt high-performance RISC CPU core.

●8-bit microcomputer control chip

●8Kx 14 program memory (flash memory)

●368-byte data memory and 256-byte EEPROM data memory.

●5 groups of I/O ports (A, B, C, D, E)

● Two groups of 8-bit timer 0, timer 2 and 1 group 16-bit timer 1.

● Support 14 interrupt handling.

1.3 MPLAB

MPLAB is an integrated development environment (IDE) developed by Microchip company for PIC series single chip computers. Mplab includes the following tools:

Mplab editor-program editor

Mpasm assembler-program assembler

Mplab-sim software simulator-software simulator

Mplab-IC emulator-hardware emulator

Debugging simulation environment of mplab-ICD-ICD components.

Two system architecture

2. 1 PIC 16F87X MCU core architecture

PIC series single chip microcomputer is a RISC architecture single chip microcomputer. The biggest difference between Harvard architecture and Von Neumann architecture used by single chip microcomputer in the past is the change of bus. Von Neumann structure is a traditional monolithic structure. Program memory and data memory are in the same memory block, and only one bus is used between the memory and CPU. The bus is used to access program memory or data memory. Therefore, to complete an instruction, it is usually necessary to use the bus in turn, from instruction acquisition, decoding, data reading and execution to data writing. The end result is that most instructions need to wait several cycles to complete. Harvard structure improves this shortcoming, mainly because program memory and data memory use different memory blocks and have their own independent buses. This greatly improves the bandwidth of instruction execution, and two buses can work at the same time. The biggest advantage is that when one instruction is being executed, the next instruction can already be captured, so the running efficiency will be significantly improved.

2.2 internal structure diagram

Fig. 2.2 is the internal functional architecture diagram of PIC 16F877 single chip microcomputer, which illustrates the connection mode between the bus and each functional block. Using the architecture diagram, we can better understand the whole system.

2.3 pin function description

The pin function and description of PIC 16F877 microcontroller are as follows.