Digital Inputs And Outputs - Digilent chipKIT MX3 Reference Manual

chipKIT™ MX3 Board Reference Manual
See the Pinout Tables below for more information about connecting peripheral modules and other devices to the
chipKIT MX3. These tables indicate the mapping between pins on the PIC32MX320 microcontroller and the pins on
the various connectors.
The PIC32 microcontroller can source or sink a maximum of 18mA on all digital I/O pins. However, to keep the
output voltage within the specified input/output voltage range (V 0.4V, V 2.4V) the pin current must be
OL OH
restricted to +7/-12mA. The maximum current that can be sourced or sunk across all I/O pins simultaneously is +/-
200mA. The maximum voltage that can be applied to any digital I/O pin is 5.5V. For more detailed specifications,
refer to the PIC32MX3XX/4XX Data Sheet.
4

Digital Inputs and Outputs

The chipKIT MX3 board provides access to 40 of the I/O pins from the PIC32 microcontroller via the Pmod
2 2
connectors. Two additional I/O pins can be accessed via the I C connector, J2. Any of the pins on the Pmod or I C
2
connectors can be individually accessed for digital input or output. Note that when the I C signals on J2 are being
2
used for I C communications, they are not available for general purpose I/O.
On PIC32 microcontrollers, the input/output pins are grouped into I/O Ports and are accessed via peripheral
registers in the microcontroller. There are seven I/O Ports numbered A–G and each is 16 bits wide. Depending on
the particular PIC32 microcontroller, some of the I/O Ports are not present, and not all 16 bits are present in all I/O
Ports.
Each I/O Port has four control registers: TRIS, LAT, PORT, and ODC. The registers for I/O Port A are named TRISA,
LATA, PORTA and ODCA. The registers for the other I/O Ports are named similarly.
The TRIS register is used to set the pin direction. Setting a TRIS bit to 0 makes the pin an output. Setting the TRIS
bit to 1 makes the pin an input.
The LAT register is used to write to the I/O Port. Writing to the LAT register sets any pins configured as outputs.
Reading from the LAT register returns the last value written.
The PORT register is used to read from the I/O Port. Reading from the PORT register returns the current state of all
of the pins in the I/O Port. Writing to the PORT register is equivalent to writing to the LAT register.
PIC32 microcontrollers allow any pin set as an output to be configured as either a normal totem-pole output or as
an open-drain output. The ODC register is used to control the output type. Setting an ODC bit to 0 makes the pin a
normal output and setting it to 1 makes the pin an open drain output.
Refer to the PIC32MX3XX/4XX Family Data Sheet, and the PIC32 Family Reference Manual, Section 12, IO Ports, for
more detailed information about the operation of the I/O Ports in the microcontroller.
The MPIDE system uses logical pin numbers to identify digital I/O pins on the connectors. These pin numbers start
with pin 0 and are numbered up consecutively.
On the chipKIT MX3, pin numbers 0–39 are used to access the pins on the Pmod connectors and pin numbers 40
2
and 41 are used for the two signal pins on the I C connector. The pin numbers are assigned so that connector JA
pin 1 (JA-01) is digital pin 0, JA pin 2 (JA-02) is digital pin 1, and so on.
Copyright Digilent, Inc. All rights reserved.
Page 7 of 24
Other product and company names mentioned may be trademarks of their respective owners.