Front Panel I/O Connectivity Design Guide

2.2.2 Switch/LED Connector Features

2.2.2.1 Hard Drive Activity LED

Connecting pins 1 and 3 to a front panel mounted LED provides visual indication that data is being

read from or written to the hard drive. For the LED to function properly, an IDE drive should be

connected to the onboard IDE interface. The LED will also show activity for devices connected to

the SCSI (hard drive activity LED) connector.

2.2.2.2 Power / Sleep / Message Waiting LED

Connecting pins 2 and 4 to a single- or dual-color, front panel mounted LED provides power on/off,

sleep, and message waiting indication. Table 2 shows the possible states for a single-color LED.

Table 3 shows the possible states for a dual-color LED.

2.2.2.3 Reset Switch

Supporting the reset function requires connecting pins 5 and 7 to a momentary-contact switch that

is normally open. When the switch is closed, the board resets and runs POST.

2.2.2.4 Power Switch

Supporting the power on/off function requires connecting pins 6 and 8 to a momentary-contact

switch that is normally open. The switch should maintain contact for at least 50 ms to signal the

power supply to switch on or off. The time requirement is due to internal debounce circuitry. After

receiving a power on/off signal, at least two seconds elapses before the power supply recognizes

another on/off signal.

Table 2. States for a Single-Color Power LED

LED State Description ACPI State

Off Sleeping or power off (not running) S1, S3, S5

Steady Green Running S0

Blinking Green Running/message waiting S0

Table 3. States for a Dual-Color Power LED

LED State Description ACPI State

Off Power off S5

Steady Green Running S0

Blinking Green Running/message waiting S0

Steady Yellow Sleeping S1, S3

Blinking Yellow Sleeping/message waiting S1, S3

 NOTE

To use the message waiting function, ACPI should be enabled in the operating system and a

message-capturing application should be invoked.