AT43USB325 datasheet(30/109 Pages) ATMEL

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3355C–USB–4/05

AT43USB325

from an interrupt, it will always return to the main program and execute one more instruction

before any pending interrupt is served.

4.11.1

MCU Control Register – MCUCR

• Bit 7, 6 – Res: Reserved Bits

• Bit 5 – SE: Sleep Enable

The SE bit must be set (1) to make the MCU enter the sleep mode when the SLEEP instruction

is executed. To avoid the MCU entering the sleep mode, unless it is the programmer's purpose,

it is recommended to set the Sleep Enable SE bit just before the execution of the SLEEP

instruction.

• Bit 4 – SM: Sleep Mode

This bit selects between the two available sleep modes. When SM is cleared (zero), Idle Mode is

selected as Sleep Mode. When SM is set (1), Power Down mode is selected as sleep mode. The

AT43USB325 does not support the Idle Mode and SM should always be set to one when enter-

ing the Sleep Mode.

• Bit 3, 2 – ISC11, ISC10: Interrupt Sense Control 1 Bit 1 and Bit 0

The External Interrupt 1 is activated by the external pin INT1 if the SREG I-flag and the corre-

sponding interrupt mask in the GIMSK is set. The level and edges on the external INT1 pin that

activate the interrupt are defined in the following table:

Bit

$35 ($55)

–

ISC11

ISC10

–

MCUCR

Read/Write

R/W

Initial Value

Table 4-2.

INT1 Sense Control

ISC11

ISC10

Description

The low level of INT1 generates an interrupt request.

Reserved.

The falling edge of INT1 generates an interrupt request.

The rising edge of INT1 generates an interrupt request.

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