Datasheet

chipKIT™ Pro MX7 Board Reference Manual

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Page 7 of 35

2.1 RESET

A reset button is at the upper right corner of the board. Pressing this button will reset the PIC32 microcontroller.

3 Pmod™ Connectors

The chipKIT Pro MX7 has six connectors for connecting Digilent Pmod peripheral modules. The Pmod connectors

labeled JA–JF, are 2x6 pin, right-angle, female pin header connectors. Each connector has an associated power

select jumper block labeled JPA–JPF.

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, various kinds of RF interfaces, 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 Pro MX7 are twelve pin connectors.

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

connectors provide eight I/O signals, two power pins, 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 pins on the Pmod connector. They are switchable between either the unregulated

power supply, VCC5V0, or the 3.3V main board supply, VCC3V3. Place the shorting block in the 3V3 position for

regulated 3.3V and in the 5V0 position to use the unregulated supply.

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.

The 200 ohm resistor in series with each I/O pin limits the amount of current that can be sourced from the

microcontroller pins. There will be a 200mV voltage drop per mA of current sourced by the pin. This will not be a

problem when driving typical, high impedance, logic inputs, but can be problematic when trying to drive low

impedance inputs. In some cases it may be necessary to use external buffers when trying to drive low impedance

inputs.

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.