This can be very helpful when one has a high priority interrupt that they just don't want to miss, or be delayed in processing. The Xmegas have a three tier priority interrupt system.
The Event System is an alternative triggering mechanism for intra-module data transfer which doesn't require the used of polled code, or interrupts. With many of the Mega/Tiny chips being produced in a smaller die size, many of the Meg/Tiny chips have a lower I/O current limit these days. If one is use to the MegaTiny 20 (40) mA pin drive capability, then look carefully at the Xmega spec's, it is less. The Version I Dragons, (without the mounting holds on the Dragon), may have difficulty programming Xmegas. The STK600 has the PDI mode, but may require a bunch of "top plates" ( ? ) for the chip of interest. The ubiquitous STK500 lacks the PDI programming mode. The only known way to "Brick" an Xmega is to set the BOD to a voltage higher than the operating voltage, in which case the BOD will hold the Xmega in reset. (One could add them via header, solder bridge, etc., after the uC is programmed.)
If you are use to putting an external R or RC on the Mega/Tiny Reset\ pin, think twice before doing so on the Xmegas.ĭoing so will/may interfere with PDI programming. These pins are not available for general purpose I/O, they are dedicated programming / debug pins. Unlike the Megas and Tinies that use ISP for programing, the Xmegas use a 2 pin PDI interface. The inputs have diode clamps, but look at your interface carefully, if needed.ģ - 3.3 V operation may not reliably, (or at all), drive a 5 V peripheral's input "High". The Inputs are not designed for use with 5 V peripherals.
The Xmegas always start up at 2 MHz, so one can't select a clock source that doesn't exist. Mention in the Clock discussion that the most common way to "brick" a Mega/Tiny, by selecting a non-existent clock source, has been eliminated in the Xmega lineup.
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