Chameleon-PIC Nurve Networks, Chameleon-PIC Datasheet - Page 158

• 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

19.1.1 Basic SPI Communications Steps
Figures 19.2(a) and (b) show the complete timing diagrams for all variants of clock polarity (CPOL) and clock phase
(CPHA). You must adhere to these timing constraints during communications. In most cases, you will use mode 0 since
it’s the default that most SPI devices boot with.
The good news is this is all taken care of by the PIC24, in fact, most PIC microcontrollers have complete SPI (and I
hardware built in that take care of all the details of both transmission and reception. The only thing we have to do as
programmers is set the hardware up, then send and receive bytes (and maybe handle an interrupt or two). Thus, working
with SPI in the PIC24 is very easy. Nonetheless, the library module we developed wraps the SPI hardware with a thin
layer of functions, so that you don’t have to deal with it all yourself. However, it’s good to understand the protocol if you
need to manually build a SPI interface with I/O pins. For example, maybe you need (4) SPI interfaces all at the same time
on the Chameleon’s expansion port, the only way to do this will be to do it manually with pin toggling.
Figure 19.3(a) – SPI timing diagrams for clock phase polarity (CPHA=0).
Figure 19.3(b) – SPI timing diagrams for clock phase polarity (CPHA=1).
© 2009 NURVE NETWORKS LLC “Exploring the Chameleon PIC 16-Bit”
2
C)
158