Chameleon-PIC Nurve Networks, Chameleon-PIC Datasheet - Page 23

• Manufacturer Part Number: Chameleon-PIC
• Description: MCU, MPU & DSP Development Tools PIC24 & PROPELLER DEV SYSTEM (SBC)
• Manufacturer: Nurve Networks

Specifications of Chameleon-PIC

• Processor To Be Evaluated: PIC24
• Data Bus Width: 16 bit
• Interface Type: USB, VGA, PS/2, I2C, ISP, SPI
• Operating Supply Voltage: 3.3 V, 5 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Referring to Figure 1.6, the program memory is divided into regions as you can see, most of them are pretty self
explanatory. The first 512 locations provide reset and interrupt vectors. There is no moving these around since they are
hardwired in. The next section is the User Program Memory that provides 43,776 (minus reset and interrupt vectors) of
single word instructions for your usage. Since the program counter is 24-bits wide, we have a lot of extra space that is
mostly filled with 0’s or reserved sections that map to nothing. Possibly as more variants of the PIC24s come out they
could be filled with more space for user programs.
Our Data (SRAM) memory is segmented as illustrated in Figure 1.6. One thing that can be gleamed from the figure is that
the PIC24 is using a little endian memory style. Just like the program memory, we don’t have free reign of the entire
memory space and certain sections of RAM will always map to special registers. The first section is the SFR region. The
SFR acronym stands for the Special Function Registers. This includes things like I/O Port control and latch registers, SPI
configuration registers, etc.
The PIC C compiler is based on the GNU GCC tool chain and thus is not the best optimizing compiler on the planet, but
isn’t bad. Hence, our approach will be to use C primarily for our coding and any time critical performance code you will
want to write in assembly language if you need to. But, we want to rely on C as much as possible for ease of use. ASM
should be used for drivers when necessary via APIs that can be called from C. Additionally, the Ardunio tool chain uses
C/C++ as well. Even though the Ardunio folks call the language “Processing”, it’s just good old C/C++!!!
NOTE
The tool of choice for native PIC development is of course MPLAB. This tool was
developed by Microchip and supports source level debugging, various programmer and
ICE debuggers etc. However, the C compiler is a plug in based on GNU GCC called
“PIC24 C compiler” sometimes also referred to as “pic30 compiler”. We will discuss
the installation of the tool chain shortly, but keep in mind the separation. Additionally, we
will be using straight “C” for coding.
Figure 1.7 – Microchip MPLAB in action.
© 2009 NURVE NETWORKS LLC “Exploring the Chameleon PIC 16-Bit”
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