W83627DHG Datasheet, PDF (178/268 Pages) Winbond – WINBOND LPC I/O

W83627DHG
14.1.2 AC Power Failure Resume
By definition, AC power failure means that the standby power is removed. The power failure resume
control logic of the W83627DHG is used to recover the system to a pre-defined state after AC power
failure. Two control bits at Logical Device A, CR[E4h], bits[6:5] indicate the pre-defined state. The
definition of these two bits is listed in the following table:
LOGICAL DEVICE A, CR[E4H],
BITS[6:5]
DEFINITION
00
System always turns off when it returns from AC power failure
01
System always turns on when it returns from AC power failure
10
System turns off / on when it returns from power failure depending
on the state before the power failure. (Please see Note 1)
11
User defines the state before the power failure. (The previous
state is set at CRE6[4]. Please see Note 2)
Note1. The W83627DHG detects the state before power failure (on or off) through the SUSB# signal and the 3VCC
power. The relation is illustrated in the following two figures.
3VCC
SUSB#
Figure 14.3 The previous state is “on” - 3VCC falls to 2.6V and SUSB# keeps at 2.0V
3VCC
SUSB#
Figure 14.4 The previous state is “off” - 3VCC falls to 2.6V and SUSB# keeps at 0.8V
Note 2.
LOGICAL DEVICE A, CR[E6H]
BIT [4]
DEFINITION
0
User defines the state to be “on”
1
User defines the state to be “off”
To ensure that VCC does not fall faster than VSB in various ATX Power Supplies, the W83627DHG adds the
option of “user define mode” for the pre-defined state before AC power failure. BIOS can set the pre-defined state
-166-
Publication Release Date: Aug, 22, 2007
Version 1.4