Lenovo ThinkPad 560E TP 560Z Technical Reference Manual - Page 45

Miscellaneous System Functions and Ports, Nonmaskable Interrupt (NMI), Attention

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Miscellaneous System Functions and Ports This section provides information about nonmaskable interrupts (NMIs), the power-on password, and hardware compatibility. Nonmaskable Interrupt (NMI) The NMI signals the system microprocessor that a parity error or a channel check timeout has occurred. This situation can cause lost data or an overrun error on some I/O devices. The NMI masks all other interrupts. The interrupt return (IRET) instruction restores the interrupt flag to the state it was in before the interrupt occurred. A system reset causes a reset of the NMI. The NMI requests from system board parity and channel check are subject to mask control with the NMI mask bit in the RT/CMOS Address register. See "RT/CMOS Address and NMI Mask Register (X'0070')" on page 2-18. The power-on default of the NMI mask is 1 (NMI disabled). Before the NMI is enabled after a power-on reset, the parity-check states are initialized by POST. Attention The operation following a write to X'0070' should access X'0071'; otherwise, intermittent failures of the RT/CMOS RAM can occur. ThinkPad 560Z System Board 2-27

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Miscellaneous System Functions and Ports
This section provides information about nonmaskable interrupts
(NMIs), the power-on password, and hardware compatibility.
Nonmaskable Interrupt (NMI)
The NMI signals the system microprocessor that a parity error or a
channel check timeout has occurred.
This situation can cause lost
data or an overrun error on some I/O devices.
The NMI masks all
other interrupts.
The interrupt return (IRET) instruction restores the
interrupt flag to the state it was in before the interrupt occurred.
A
system reset causes a reset of the NMI.
The NMI requests from system board parity and channel check are
subject to mask control with the NMI mask bit in the RT/CMOS
Address register.
See “RT/CMOS Address and NMI Mask Register
(X
'
0070
'
)” on page
2-18.
The power-on default of the NMI mask is
1 (NMI disabled).
Before the NMI is enabled after a power-on reset,
the parity-check states are initialized by POST.
Attention
The operation following a write to X
'
0070
'
should access
X
'
0071
'
; otherwise, intermittent failures of the RT/CMOS RAM
can occur.
ThinkPad 560Z System Board
2-27