9.2.5 Digital Input Enable and Sleep Modes
As shown in Figure 9-2, the digital input signal can be clamped to ground at the input of the schmitt-trigger. The signal
denoted SLEEP in the figure, is set by the MCU sleep controller in power-down mode, power-save mode, and standby mode
to avoid high power consumption if some input signals are left floating, or have an analog signal level close to VCC/2.
SLEEP is overridden for port pins enabled as external interrupt pins. If the external interrupt request is not enabled, SLEEP
is active also for these pins. SLEEP is also overridden by various other alternate functions as described in Section 9.3
“Alternate Port Functions” on page 55.
If a logic high level (“one”) is present on an asynchronous external interrupt pin configured as “Interrupt on Rising Edge,
Falling Edge, or Any Logic Change on Pin” while the external interrupt is not enabled, the corresponding external interrupt
flag will be set when resuming from the above mentioned sleep modes, as the clamping in these sleep modes produces the
requested logic change.
9.3
Alternate Port Functions
Most port pins have alternate functions in addition to being general digital I/Os. Figure 9-5 shows how the port pin control
signals from the simplified Figure 9-2 can be overridden by alternate functions. The overriding signals may not be present in
all port pins, but the figure serves as a generic description applicable to all port pins in the AVR® microcontroller family.
ATmega16/32/64/M1/C1 [DATASHEET]
55
7647O–AVR–01/15
MICROCHIP [ MICROCHIP ]
