ATTINY5_14 Datasheet, PDF (44/170 Pages) ATMEL Corporation – Atmel 8-bit AVR Microcontroller

Figure 10-5. Synchronization when Reading a Software Assigned Pin Value
SYSTEM CLK
r16
0xFF
INSTRUCTIONS
out PORTx, r16
nop
in r17, PINx
SYNC LATCH
PINxn
r17
0x00
t _pd
0xFF
10.2.5 Digital Input Enable and Sleep Modes
As shown in Figure 10-2 on page 41, 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 and Standby
modes to avoid high power consumption if some input signals are left floating, or have an analog signal level close
to V_CC/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
“Alternate Port Functions” on page 45.
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 mode, as the clamping in these
sleep mode produces the requested logic change.
10.2.6 Unconnected Pins
If some pins are unused, it is recommended to ensure that these pins have a defined level. Even though most of
the digital inputs are disabled in the deep sleep modes as described above, floating inputs should be avoided to
reduce current consumption in all other modes where the digital inputs are enabled (Reset, Active mode and Idle
mode).
The simplest method to ensure a defined level of an unused pin, is to enable the internal pull-up. In this case, the
pull-up will be disabled during reset. If low power consumption during reset is important, it is recommended to use
an external pull-up or pulldown. Connecting unused pins directly to V_CC or GND is not recommended, since this
may cause excessive currents if the pin is accidentally configured as an output.
ATtiny4/5/9/10 [DATASHEET] 44
8127F–AVR–02/2013