It has 54 digital input/output pins (of which 15 can be used as PWM outputs), 16 analog inputs, 4 UARTs (hardware serial ports), a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button. However I don't recall reading in AVR mega datasheets about their recommendations for unused input pins, probably because it doesn't lead to device failures, just possible faulty hardware logic/software symptoms. The Arduino Mega 2560 is a microcontroller board based on the ATmega2560. Then when pure CMOS logic chips started becoming popular in the 70s and beyond a lot of us learned first hand what happens if you allowed 'floating inputs' on the earlier CMOS chip designs, which was chip self oscillation and very hot running and even burning up the chip and a few of my finger tips at the time.īottom line, be sure to review the specific datasheet of any logic chip you are using as to how to handle unused input pins. This RPS (regulated power supply) provides the power to the microcontroller as well as other components which are used over the Arduino mega board. For 12V into Vin that works out to 1/(12-5) 1/7 or 143mA. So the max current is 1W / (Vsupply - 5V). The max recommended dissipation for the regulator is 1 Watt. If powered through the power plug or Vin the 5V comes from the little 5V regulator on the board. To the best of my memory these earlier TTL families had unconnected inputs pulled up HIGH internally but good design practice would wire all unused inputs to either of the power rails as required. These pins are used for providing o/p regulated voltage approximately 5V. For the 5V it depends on the power source. I worked (field troubleshooting) with a whole lot of TTL, 74xx, 74LSxx, 74Hxx, 74Sxx in the 70s and 80s. Not like older TTL inputs, which generally could be relied on to be a low if left unconnected.
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