Academic Program

Digital I/O

Digital I/O

Almost every pin on the Enhance Mid-Range PIC MCU can be used as a digital input or output pin. Digital Pins share these attributes:

  • Monitor Digital Inputs
  • Control Digital Devices
  • Internal Weak Pull-ups
  • Multiplexed with Peripherals
  • High Drive Capability (up to 25 mA sink/source on many I/O pins)
  • Direct single cycle bit manipulation
  • 4 kV ESD protection diodes

At Reset:

  • Digital Pins revert to input (Hi-Z)
  • Analog Capable pins revert to analog

Typical Digital Pin Structure

Five registers control the operation of a digital pin. These 8-bit registers control 8 pins of a PORT. Using the registers TRISX, PORTx, LATx, WPUx, and ANSEL the program can:

  • Configure a pin as an input or output TRISx
  • Read an input pin (or all 8 PORT pins) PORTx
  • Output a 1 or 0 to a pin LATx
  • Enable or disable the internal Pull Up Resistor WPUx
  • Determine if analog capable pins operate in analog or digital Mode ANSEL

basic-digital-io.png

 

Multiplexed Pins

In addition to being configured as digital I/Os, pins on enhanced mid-range PIC MCUs can have several possible functions. The pin diagram on the datasheet shows the options for each pin. At start-up, the program has the option of configuring the pins.

multiplexed.png