Datasheet

 2018 Microchip Technology Inc. Data Sheet Complete DS40002060A-page 54

ATtiny4/5/9/10

When reading back a software assigned pin value, a nop instruction must be inserted as indicated in Figure 11-5 on page

54. The out instruction sets the “SYNC LATCH” signal at the positive edge of the clock. In this case, the delay tpd through

the synchronizer is one system clock period.

Figure 11-5. Synchronization when Reading a Software Assigned Pin Value

11.2.5 Digital Input Enable and Sleep Modes

As shown in Figure 11-2 on page 51, 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

/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 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 mode, as the clamping in these sleep mode produces the

requested logic change.

11.2.6 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 con-

sumption 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

or GND is not recommended, since this may cause excessive cur-

rents if the pin is accidentally configured as an output.

out PORTx, r16 nop in r17, PINx

0xFF

0x00 0xFF

SYSTEM CLK

r16

INSTRUCTIONS

SYNC LATCH

PINxn

r17