System Support

4.6.2 GPIO Functions

PCH-DO Functions

The PCH-D0 provides various functions through the use of programmable general purpose input/output (GPIO) ports. These systems use GPIO ports and associate registers of the PCH for the following functions:

■PCI interrupt request control

■Chassis and board ID

■Hood (cover) sensor and lock detect

■Media card reader detect

■S4 state indicator

■USB port over-current detect

■Flash security override

■Serial port detect

■REQn#/GNTn# sigal control

■Password enable

■Boot block enable

SIO Controller Functions

In addition to the serial and parallel port functions, the SIO controller provides the following specialized functions through GPIO ports:

■Power/Hard drive LED control for indicating system events (refer to Table 4-8)

■Hood lock/unlock controls the lock bar mechanism

■Thermal shutdown control turns off the CPU when temperature reaches certain level

■Processor present/speed detection detects if the processor has been removed. The occurrence of this event will, during the next boot sequence, initiate the speed selection routine for the processor.

■Legacy/ACPI power button mode control uses the pulse signal from the system's power button and produces the PS On signal according to the mode (legacy or ACPI) selected. Refer to chapter 7 for more information regarding power management.

Technical Reference Guide

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