Datasheet

53
7701F–AVR–10/12
Atmel ATtiny24/44/84 [Preliminary]
11.2 Register Description
11.2.1 MCUCR – MCU Control Register
The External Interrupt Control Register A contains control bits for interrupt sense control.
• Bits 1, 0 – ISC01, ISC00: Interrupt Sense Control 0 Bit 1 and Bit 0
The External Interrupt 0 is activated by the external pin INT0 if the SREG I-flag and the corre-
sponding interrupt mask are set. The level and edges on the external INT0 pin that activate the
interrupt are defined in Table 11-1 on page 53. The value on the INT0 pin is sampled before
detecting edges. If edge or toggle interrupt is selected, pulses that last longer than one clock
period will generate an interrupt. Shorter pulses are not guaranteed to generate an interrupt. If
low level interrupt is selected, the low level must be held until the completion of the currently
executing instruction to generate an interrupt.
11.2.2 GIMSK – General Interrupt Mask Register
• Bits 7, 3..0 – Res: Reserved Bits
These bits are reserved bits in the ATtiny24/44/84 and will always read as zero.
• Bit 6 – INT0: External Interrupt Request 0 Enable
When the INT0 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), the
external pin interrupt is enabled. The Interrupt Sense Control0 bits 1/0 (ISC01 and ISC00) in
the External Interrupt Control Register A (EICRA) define whether the external interrupt is acti-
vated on rising and/or falling edge of the INT0 pin or level sensed. Activity on the pin will cause
an interrupt request even if INT0 is configured as an output. The corresponding interrupt of
External Interrupt Request 0 is executed from the INT0 Interrupt Vector.
• Bit 5 – PCIE1: Pin Change Interrupt Enable 1
When the PCIE1 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), pin
change interrupt 1 is enabled. Any change on any enabled PCINT11..8 pin will cause an inter-
rupt. The corresponding interrupt of Pin Change Interrupt Request is executed from the PCI1
Interrupt Vector. PCINT11..8 pins are enabled individually by the PCMSK1 Register.
Bit 76543210
0x35 (0x55)
BODS PUD SE SM1 SM0 BODSE ISC01 ISC00 MCUCR
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Table 11-1. Interrupt 0 Sense Control
ISC01 ISC00 Description
0 0 The low level of INT0 generates an interrupt request.
0 1 Any logical change on INT0 generates an interrupt request.
1 0 The falling edge of INT0 generates an interrupt request.
1 1 The rising edge of INT0 generates an interrupt request.
Bit 76543210
0x3B (0x5B) – INT0 PCIE1 PCIE0 – – – – GIMSK
Read/Write R R/W R/W R/w R R R R
Initial Value 0 0 0 0 0 0 0 0