PIC18F Interrupt I/O, LCD, and Keyboard Interfacing
Mohamed Rafiquzzaman · 2017
This chapter describes the basics of polled and interrupt input/output (I/O). Topics include PIC18F polled and interrupt I/O using both assembly and C. The chapter covers techniques associated with interfacing the PIC18F4321 to a typical liquid crystal display (LCD), such as the Hitachi HD44780, and a hexadecimal keyboard. The chapter describes the basics of interfacing the PIC18F4321 microcontroller to a hexadecimal keyboard and a seven-segment display. PIC18F interrupts are basically divided into two types, namely external and internal interrupts. The process of handling interrupt I/O is very similar in concept to subroutine CALL and RETURN instructions. The PIC18F has the flexibility of changing the triggering levels to a trailing edge via programming a register. The PIC18F4321 interrupts can be classified into two groups: high priority interrupt levels and low priority interrupt levels.