Digital Inputs And Outputs - Digilent chipKIT Pro MX7 Reference Manual

chipKIT™ Pro MX7 Board Reference Manual
Digilent Pmods can either be plugged directly into the ports on the chipKIT Pro MX7 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 MX7. These tables describe the mapping between pins on the PIC32MX795 microcontroller and
the pins on the various ports.
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. The maximum voltage that can be
applied to any analog input capable pin is 3.6V. For more detailed specifications, refer to the
PIC32MX5XX/6XX/7XX Family Data Sheet.
4

Digital Inputs and Outputs

The chipKIT Pro MX7 board provides access to 48 of the I/O pins from the PIC32MX795 microcontroller via the
2
Pmod ports. Four additional I/O pins can be accessed via the I C connectors, J7 and J8. Any of the pins on the Pmod
2 2
or I C ports can be individually accessed for digital input or output. Note that when the I C signals on J7 or J8 are
2
being 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 of the ports are 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 associated 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 PIC32MX5XX/6XX/7XX Family Data Sheet, and the PIC32 Family Reference Manual, Section 12, I/O
Ports, for more detailed information about the operation of the I/O Ports in the microcontroller.
Pmod port JF, pins 8, 9, and 10 are connected to the signals TCK/RA1, TDI/RA4, and TDO/RA5 respectively. These
microcontroller pins are shared between general purpose I/O functions and use by the JTAG controller. The JTAG
controller is enabled on reset, so these pins are not available for general purpose I/O until the JTAG controller is
disabled. The following statement can be used to disable the JTAG controller:
DDPCONbits.JTAGEN = 0;
The JTAG controller is disabled by the startup initialization code in the MPIDE runtime. It is not necessary to disable
the JTAG controller when using the board with MPIDE.
Copyright Digilent, Inc. All rights reserved.
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