AT90LS8535_14 Datasheet, PDF (28/127 Pages) ATMEL Corporation – Data and Nonvolatile Program Memories

External Interrupts
• Bit 5 – ICF1: Input Capture Flag 1
The ICF1 bit is set (one) to flag an input capture event, indicating that the
Timer/Counter1 value has been transferred to the Input Capture Register (ICR1). ICF1
is cleared by hardware when executing the corresponding interrupt handling vector.
Alternatively, ICF1 is cleared by writing a logical “1” to the flag. When the SREG I-bit
and TICIE1 (Timer/Counter1 Input Capture Interrupt Enable) and ICF1 are set (one), the
Timer/Counter1 Capture Interrupt is executed.
• Bit 4 – OCF1A: Output Compare Flag 1A
The OCF1A bit is set (one) when compare match occurs between the Timer/Counter1
and the data in OCR1A (Output Compare Register 1A). OCF1A is cleared by hardware
when executing the corresponding interrupt handling vector. Alternatively, OCF1A is
cleared by writing a logical “1” to the flag. When the I-bit in SREG and OCIE1A
(Timer/Counter1 Compare Match InterruptA Enable) and the OCF1A are set (one), the
Timer/Counter1 Compare A Match Interrupt is executed.
• Bit 3 – OCF1B: Output Compare Flag 1B
The OCF1B bit is set (one) when compare match occurs between the Timer/Counter1
and the data in OCR1B (Output Compare Register 1B). OCF1B is cleared by hardware
when executing the corresponding interrupt handling vector. Alternatively, OCF1B is
cleared by writing a logical “1” to the flag. When the I-bit in SREG and OCIE1B
(Timer/Counter1 Compare Match InterruptB Enable) and the OCF1B are set (one), the
Timer/Counter1 Compare Match B Interrupt is executed.
• Bit 2 – TOV1: Timer/Counter1 Overflow Flag
The TOV1 is set (one) when an overflow occurs in Timer/Counter1. TOV1 is cleared by
hardware when executing the corresponding interrupt handling vector. Alternatively,
TOV1 is cleared by writing a logical “1” to the flag. When the I-bit in SREG and TOIE1
(Timer/Counter1 Overflow Interrupt Enable) and TOV1 are set (one), the
Timer/Counter1 Overflow Interrupt is executed. In up/down PWM mode, this bit is set
when Timer/Counter1 advances from $0000.
• Bit 1 – Res: Reserved Bit
This bit is a reserved bit in the AT90S8535 and always reads zero.
• Bit 0 – TOV0: Timer/Counter0 Overflow Flag
The bit TOV0 is set (one) when an overflow occurs in Timer/Counter0. TOV0 is cleared
by hardware when executing the corresponding interrupt handling vector. Alternatively,
TOV0 is cleared by writing a logical “1” to the flag. When the SREG I-bit and TOIE0
(Timer/Counter0 Overflow Interrupt Enable) and TOV0 are set (one), the
Timer/Counter0 Overflow Interrupt is executed. In up/down PWM mode, this bit is set
when Timer/Counter1 advances from $0000.
The external interrupts are triggered by the INT1 and INT0 pins. Observe that, if
enabled, the interrupts will trigger even if the INT0/INT1 pins are configured as outputs.
This feature provides a way of generating a software interrupt. The external interrupts
can be triggered by a falling or rising edge or a low level. This is set up as indicated in
the specification for the MCU Control Register (MCUCR). When the external interrupt is
enabled and is configured as level-triggered, the interrupt will trigger as long as the pin
is held low.
The external interrupts are set up as described in the specification for the MCU Control
Register (MCUCR).
28 AT90S/LS8535
1041H–11/01