80 MHz CLOCK
+ 3.3V part. However, it can accept +5V logic level inputs
on certain pins (see Figure 2 +5V tolerant pins) without
damage. The chip is organized around two internal buses.
The top bus is the faster of the two and runs at the
system clock CPU rate. It allows simultaneous
communications for devices on this bus without any bus
contention. Some of the devices here are the 32 Core
CPU, the eight channel DMA (Direct Memory Access
Controller), and USB. Other components on this bus are
Flash, RAM, interrupt controller, all the digital ports, and
a peripheral bridge (a connection to all the on-chip
peripherals). It is interesting to note that digital ports
reside on the high-speed bus. This means they can be
toggled (on/off) at the 80 MHz rate —-able to generate
digital signals of up to 40 MHz if needed. With the use of
the DMA, this port (or any other peripheral) can directly
access memory without CPU (software) intervention for
data transfers. We will show the DMA in action with one
of the experiments here.
An Overview of 32-Bit
A block diagram of the Experimenter is shown in
Figure 3; schematics are included towards the end of
the article. The board has extensive expansion capabilities.
This approach allows access to all the PIC32MX695F512H
I/O for experiments. The Experimenter inside connectors are
.100” female headers. This allows you to mount expansion
cards right on top of the Experimenter (vertical expansion).
The left side female header top and bottom set has an
Arduino expansion footprint that is mechanically and
electrically compatible with Arduino expansion cards; the
FIGURE 3. EXP32 block diagram.
FIGURE 4. Experimenter expansion.
minor exceptions to this interface are shown in red in
Figure 5. These expansion cards are available from a
number of vendors and this feature allows users the
opportunity to integrate a number of existing Arduino
expansion cards with their Experimenter applications. Keep
in mind that new software drivers will have to be rewritten
February 2011 59