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Reset
5.1
5.1.1
5.1.2
Note: This method does not work under operating systems that trap calls to this BIOS function.
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This chapter discusses the reset types and reset sources on the ZT 5515. If necessary, the ZT 5515's
board reset characteristics can be tailored to the requirements of a specific system.
Reset Types and Sources
The ZT 5515's reset types are listed below. The sources for each reset type are detailed in the
following topics.
•
Hard Reset: All devices are held in reset.
•
Soft Reset: CPU initialization only. Other devices are not reset.
•
Backend Power Down: The backend logic is powered off. The board is powered on and is
held in reset.
•
NMI: Non-maskable interrupt. Though not a reset in the strict sense, an NMI can have the
same effect as other resets.
Hard Reset Sources
System Register CF9h (ICH4 Reset Control Register)
Bits 1 and 2 in this register are used by the ICH4 to generate a hard reset or a soft reset. During a
hard reset, the ICH4 asserts CPURST, PCIRST#, and RSTDRV. Additionally, it resets its core and
suspend well logic.
Soft Reset Sources
System Register CF9h (ICH4 Reset Control Register)
Bits 1 and 2 in this register are used by the ICH4 to generate a hard reset or a soft reset. During a
soft reset, the ICH4 asserts INIT to the CPU for 16 PCICLK. This causes the processor to enter
"real mode", initialize its internal registers, and begin instruction execution from FFFFFFF0h (the
boot vector).
Keyboard Controller Reset
The keyboard controller generates a keyboard controller reset when FEh is written to port 64h. This
causes the ICH4 to assert INIT to the CPU.
Keyboard CTRL-ALT-DEL
Simultaneously pressing these keys calls a BIOS function that reboots the system.
Watchdog Timer (System Register Address 79h)
TM
ZT 5515 Compute Processor Board Technical Product Specification
Reset
5
35
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