Atmel AT01080: XMEGA E Schematic Checklist [APPLICATION NOTE]
42087A
−
AVR
−
04/2013
5
Table 2-1. Reset circuit checklist.
Signal name
Recommended pin connection
Description
______
RESET
Reset low level threshold voltage
V
CC
= 2.7 - 3.6V: Below 0.45 × V
CC
V
CC
= 1.6 - 2.7V: Below 0.42 × V
CC
(V
CC
= 2.7V included)
Reset pin
Notes:
The pull-up resistor makes sure that reset does not go low unintended. When the PDI programming and
debugging is used, the reset line is used as clock. The reset pull-up should be 10k
Ω
or weaker, or be
removed.
The pull-down resistor prevents from overvoltage on the RESET pin when the switch is pressed.
Any reset capacitors should be removed if PDI programming and debugging is used. Other external reset
sources should be disconnected.
3.
Clocks and Crystal Oscillators
3.1
External clock source
Figure 3-1. External clock source example schematic.
Table 3-1. External clock source checklist.
Signal name
Recommended pin connection
Description
XTAL1
XTAL1 is used as input for an external clock signal
EXTCLK: input for external clock signal on
PORT R pin 1
XTAL2
Can be left unconnected or used as GPIO
PC4
PC4 is used as input for an external clock signal
EXTCLK: input for external clock signal on
PORT C pin 4
