Digilent 410-297P-KIT User Manual

Page 8

ChipKIT MX3 Board Reference Manual

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Page 8 of 25

Digilent Pmods are a line of small peripheral modules that provide various kinds of I/O interfaces. The Pmod

product line includes such things as button, switch and LED modules, connector modules, LCD displays, high

current output drivers, and many others.

There are two styles of Pmod connector: six-pin and twelve-pin. Both connectors use standard pin headers with

100mil spaced pins. The six-pin connectors have the pins in a 1x6 configuration, while the twelve-pin connectors

use a 2x6 configuration. All of the Pmod connectors on the ChipKIT MX3 are twelve pin connectors.

The six-pin connectors provide four I/O signals, ground and a switchable power connection. The twelve-pin

connectors provide eight I/O signals, two power and two ground pins. The twelve-pin connectors have the signals

arranged so that one twelve-pin connector is equivalent to two of the six-pin connectors. Pins 1–4 and 7–10 are

the signal pins, pins 5 and 11 are the ground pins and pins 6 & 12 are the power supply pins.

The pin numbering that Digilent uses on the twelve-pin Pmod connectors is non-standard. The upper row of pins

are numbered 1–6, left to right (when viewed from the top of the board), and the lower row of pins are numbered

7–12, left to right. This is in keeping with the convention that the upper and lower rows of pins can be considered

to be two six-pin connectors stacked. When viewed from the end of the connector, pin 1 is the upper right pin and

pin 7 is immediately below it (closer to the PCB).

Each Pmod connector has an associated power select jumper. These are used to select the power supply voltage

supplied to the power supply pin on the Pmod connector. They are switchable between either the regulated 5V

power supply or the 3.3V main board supply. Place the shorting block in the 3V3 position for regulated 3.3V and in

the 5V0 position for regulated 5V. Note that the 5V0 position will supply the unregulated input supply if the

regulator bypass jumper JP2 is in the BYP position.

Each signal pin on the Pmod connectors is connected to an input/output pin on the PIC32 microcontroller. Each pin

has a 200 ohm series resistor and an ESD protection diode. The series resistor provides short circuit protection to

prevent damaging the I/O block in the microcontroller if the pin is inadvertently shorted to VDD or GND, or two

outputs are shorted together. The ESD protection diode protects the I/O block from damage due to electro-static

discharge.

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 MX3 or

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

See the Pinout Tables in Appendices B–D 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

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.