gizDuino Hardware

Posted on Feb 7, 2014

The Flash-based program memory is where the program sketch is stored after an upload. The SRAM act as the main memory where program variables are temporarily stored as the sketch executes. The system clock synchronizes the internal operation of the CPU and other peripherals. Of the ATmega`s 23 programmable I/O pins, only 20 pins are available in th

gizDuino Hardware
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e Arduino. Twopins are used by the oscillator circuit and 1 pin is used by the RESET, reducing the number of available I/O pins down to 20. The system clock circuitry of the ATmega generates a clean square wave signal that is used to synchronize the operations of the CPU and peripherals inside the microcontroller. The system clock performs a function that is analogous to what a traffic light does in managing traffic in an intersection. The ATmega normally requires an external oscillator circuit where it derives the base clock. The oscillator circuit in the gizDuino board consists of a 16MHz crystal oscillator and two loading capacitors. It is connected to Pin 7 (XTAL1) and Pin 8 (XTAL2) of the ATmega, as shown below. As to be expected, this is the same circuit found in the official Arduinos. Now, a little rant: with both ATmega328 and ATmega168 rated to run at a full 20Mhz clock speed, I can not help but wonder why the Arduino team settled for a much slower 16Mhz clock. Granted that they probably choose backward-compatibility with their older boards and eliminate rewrite of the existing library routines, I still think it has to be done sooner than later. With several Arduino boards already existing, a version that runs on a full 20-Mhz speed would, at least, be nice addition. End of little rant. As already note previously, both XTAL1 and XTAL2 pins also function as programmable I/O pins. Both pins have alternative names of...

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