5 digital i/o – Digilent 410-295P-KIT User Manual

Page 10

ChipKIT Pro MX4 Reference Manual

Other product and company names mentioned may be trademarks of their respective owners.

Page 10 of 37

Although ESD protection is provided between the connector pins and the microcontroller pins, ESD safe handling

procedures should be followed when handling the circuit board. The pins on the microcontroller and other circuits

on the board are exposed and can be damaged through ESD when handling the board.

Digilent Pmod peripheral modules can either be plugged directly into the connectors on the ChipKIT Pro MX4 or

attached via cables. Digilent has a variety of Pmod interconnect cables available.

See the Pinout Tables in Appendix C, for more information about connecting peripheral modules and other devices

to the ChipKIT Pro MX4. These tables describe the mapping between pins on the PIC32MX460 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

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 only I/O pin is 5.5V. The maximum voltage that
can be applied to any analog capable I/O pin is 3.6V. For more detailed specifications, refer to the
PIC32MX3XX/4XX Family Data Sheet.

5 Digital I/O

The ChipKIT Pro MX4 board provides access to 72 of the I/O pins from the PIC32 microcontroller via the Pmod
connectors. Two additional I/O pins can be accessed via the I

C connector, J6. Any of the pins on the Pmod or I

connectors can be individually accessed for digital input or output. Note that when the I

C signals on J6 are being

used for I

C communications, they are not available for general purpose I/O. Note that the signals on I

C connector

J2 are shared with pins 1 & 2 of Pmod connector JF.
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 the output level of 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.