Digilent chipKIT Pro MX7 Reference Manual page 20

chipKIT™ Pro MX7 Board Reference Manual
If, for example, both references were selected to use external references, with 1V applied to Vref- and 2V applied
to Vref+, the input voltage range at the analog input pins would be from 1V to 2V. An applied voltage of 1V would
have a converted value of ~0, 1.5V would have a converted value of ~511, and 2V would have a converted value of
~1023.
When both external references are being used, Vref+ must have a higher voltage applied to in than Vref-.
The analog reference input pins appear on Pmod port JE, pins 9 & 10. Vref- is on pin JE-09, and Vref+ is on pin JE-
10. These pins are not available to be used for digital I/O when being used as an external reference.
When using the MPIDE software, the use of external analog references is selected using the analogReference()
function. The following values can be used with analogReference():
 DEFAULT – Vref- = 0V, Vref+ = 3.3V
 INTERNAL – same as default
 EXTERNAL – Vref- = 0V, Vref+ = voltage at A2
 EXTMINUS – Vref- = voltage at A3, Vref+ = 3.3V
 EXTPLUSMINUS – Vref- = voltage at A3, Vref+ = voltage at A2
13 Timers
The PIC32MX795 microcontroller provides five timers that can be used for various timing functions. These timers
are each 16 bits wide, although two pairs, TIMER2/TIMER3 and TIMER4/TIMER5 can be combined to produce 32
bit wide timers.
A timer consists of a control register, a counter register, and a period register. The control register is used to
configure the timer for various modes of operation. The count register counts cycles of the clock source selected
via the control register. This clock source can be the peripheral bus clock or a division of the peripheral bus clock
via a prescaler divider. The period register can be used to generate an interrupt and/or reset the count register
when a predetermined value is reached.
Each timer has an associated input pin. In some operating modes, this pin can be used as an external clock input to
the timer, or as a gate input to turn on/off incrementing of the counter register under control of an external signal.
The following gives the Pmod port position, chipKIT pin number, microcontroller I/O port, and bit number for the
timer input pins.
 T1CK – not available
 T2CK – JC-01, digital pin 16, RC01
 T3CK – not available
 T4CK – not available
 T5CK – JD-03, digital pin 26, RC04
For detailed information on the operation of the PIC32 timers, refer to the PIC32 Family Reference Manual, Section
14, Timers.
When using the MPIDE software, the symbols PIN_TCK2 and PIN_TCK5 can be used to access the timer input pins.
Control and operation of the timers is not explicitly provided in the current version of the MPIDE software. This
capability will be added in a future version of the software; however, timers are used implicitly by various core
functions and libraries.
Copyright Digilent, Inc. All rights reserved.
Other product and company names mentioned may be trademarks of their respective owners.
Page 20 of 35