Chameleon-PIC Nurve Networks, Chameleon-PIC Datasheet - Page 20

• 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

1.3 The Microchip PIC24HJ Chip
The Microchip PIC24HJ comes in a number of packages including 28-pin DIP (duel inline package). We are using the
PIC24HJ128GP502 DIP package in the Chameleon. Figure 1.4 shows the packaging and pin out of the chip. The
PIC24HJ was designed as a general purpose, high performance microcontroller with a 16-bit data path, single clock
execution on many instructions, as well as support for 32-bit operations and built in multiply instructions. The chip has a
large FLASH memory of 128K Bytes, but a smaller 8K Byte SRAM which makes a lot of RAM intensive applications
challenging; however, the Chameleon is designed for control applications and 8K of RAM should be more than enough for
anything you need. For complete details on the processor, please review the datasheet located on the DVD-ROM here:
Table 1.1 below shows the various differences between the variants of the PIC24HJxxx for reference. The PIC24HJallows
re-writing to the FLASH as well, so unused portions of FLASH can be used for storage; however, it’s not ideal to
constantly re-write FLASH since there is a limit to the number of times it can be re-written; 100,000 give or take.
Additionally, you can use the 1MByte SPI FLASH on the Chameleon as well for storage.
Figure 1.5 shows the PIC24HJ architecture in block diagram form and Table 1.2 lists the pins and their function for the
PIC24HJ128.
Pin Group
Port A (RA4:PA0) - Port A is an 5-bit bi-directional I/O port. All ports on the PIC contain Schmitt Trigger inputs for
improved noise immunity. Pins can drive from 3.0V to 3.6V and those with open drain capabilities can drive up to 5V
output. In addition pins can sink up to 4mA of current. Port A contains the external oscillator and crystal drive capabilities
so we will dedicate two pins for clocking the device. The other pins can be used for analog voltage inputs and general
purpose I/O.
DVD-ROM: \ cham_pic \ docs \ datasheets \ PIC24HJXXXXGPX06_08_10.pdf
NOTE
NOTE
FLASH memories typically have a maximum number of times they can be written;
something in the range of 10,000 to 100,000. This doesn’t mean that at 10,001 or
100,001 the memory won’t work, it just means the erase cycles and write cycles may
take longer to get the memory to clear or write. And this then degrades further as the
write/erase cycles persist. Thus, if you were to code all day and re-write your FLASH
100x times a day, then at 100,000 re-write cycles, you would have 3-4 years before you
ever saw any problems. On the other hand, if you write code to use the FLASH as a
solid state disk and constantly re-write the memory 10,000x a run, you can see how
quickly you might degrade the memory.
Since the PIC24HJ has so many internal peripherals and only a finite number of pins,
many functions are multiplexed on the I/O pins such as SPI, I2C, UARTs, A/D, D/A, etc.
In addition to pin multiplexing the PIC24 allows users to remap a number of functions to
different pins so the user has the ultimate flexibility in deciding which pin does what.
This is in contrast to the AVR that fixes the pin I/O capability. When you enable one of
the peripherals they will typically override the I/O functionality and take on the special
functions requested. However, when you don’t enable any peripherals each I/O pin is a
simple I/O pin as listed in Table 1.2.
Description
Table 1.1 - Differences between PIC24HJ 32, 64, 128.
Table 1.2 – The PIC24HJ general pin descriptions.
Device
PIC24HJ32
PIC24HJ64
PIC24HJ128
Flash
32 K Byte
64 K Byte
128 K Byte
© 2009 NURVE NETWORKS LLC “Exploring the Chameleon PIC 16-Bit”
RAM
4 K Bytes
8 K Bytes
8 K Bytes
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