W83627DHG Datasheet, PDF (66/268 Pages) Winbond – WINBOND LPC I/O

W83627DHG
7.7.3 Caseopen Detection
The purpose of Caseopen function is used to detect whether the computer case is opened. This feature
must be able to function even when there is no 3VSB power. Consequently, the power source for the
circuit is from either Pin 74 (VBAT) or Pin 61 (3VSB). 3VSB is the default power source. If there is no
3VSB power, the power source is VBAT. This is designed to save power consumption of the battery.
When the case is closed, the signal of Pin 76 must be pulled high by an externally pulled-up 2MΩ
resistor that is connected to Pin 74. Once the case is opened, the signal will be changed from high to
low. Meanwhile, the detection circuit inside the IC latches the signal. As a result, the interrupt status
and the real-time status can be read at the registers next time when the computer is booted. The status
will not be cleared unless Bank 0, Index 46h, bit 7, or CR[E6h] bit 5 at Logical Device A is set to “1” first
and then to “0”.
CASEOPEN#
CASEOPEN
CLEAR
CASEOPEN
STATUS
Figure 7.1 Caseopen Logic
Publication Release Date: Aug, 22, 2007
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Version 1.4