SC2200 NSC [National Semiconductor], SC2200 Datasheet - Page 118

• Manufacturer Part Number: SC2200
• Description: Thin Client On a Chip
• Manufacturer: NSC [National Semiconductor]

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SuperI/O Module
4.5.2.7
The system power state may be No Power, Power On,
Power Off or Power Failure. Table 4-18 indicates the power-
source combinations for each state. No other power-source
combinations are valid.
In addition, the power sources and distribution for the entire
system are illustrated in Figure 4-8 on page 117.
No Power
This state exists when no external or battery power is con-
nected to the device. This condition does not occur once a
backup battery has been connected, except in the case of
a malfunction.
Power On
This is the normal state when the system is active. This
state may be initiated by various events in addition to the
normal physical switching on of the system. In this state,
the system power supply is powered by external AC power
and produces V
are powered by V
ical device, which is powered by V
Power Off (Suspended)
This is the normal state when the system has been
switched off and is not required to be active, but is still con-
nected to a live external AC input power source. This state
may be initiated directly or by software. The system is pow-
ered down. The RTC logical device remains active, pow-
ered by V
Power Failure
This state occurs when the external power source to the
system stops supplying power, due to disconnection or
power failure on the external AC input power source. The
RTC continues to maintain timekeeping and RAM data
under battery power (V
was set in the RTC. In this case, the oscillator stops func-
tioning if the system goes to battery power, and timekeep-
ing data becomes invalid.
System Bus Lockout
During power on or power off, spurious bus transactions
from the host may occur. To protect the RTC internal regis-
ters from corruption, all inputs are automatically locked out.
The lockout condition is asserted when V
V
V
SBON
DIGITAL
+
.
SB
Table 4-18. System Power States
System Power States
.
V
DIGITAL
+
SB
DIGITAL,
and V
BAT
(Continued)
with the exception of the RTC log-
+ or -
+ or -
V
), unless the oscillator stop bit
BAT
+
SB
. The system and the part
SB.
Power State
No Power
Power Failure
Power Off
Power On
SB
is lower than
118
Power-Up Detection
When system power is restored after a power failure or
power off state (V
for a delay of 62 msec (minimum) to 125 msec (maximum)
after the RTC switches from battery to system power.
The lockout condition is switched off immediately in the fol-
lowing situations:
• If the Divider Chain Control bits, DV[2:0], (CRA bits [6:4])
• When battery voltage is below V
• If bit 7 (VRT) of CRD is 0, all input signals are enabled
4.5.2.8
The RTC oscillator is active if:
• V
-or-
• V
The RTC oscillator is disabled if:
• During power-down (V
-or-
• Software wrote 00x to DV[2:0] bits of the CRA Register
If the RTC oscillator becomes inactive, the following fea-
tures are dysfunctional/disabled:
• Timekeeping.
• Periodic interrupt.
• Alarm.
specify a normal operation mode (01x or 100), all input
signals are enabled immediately upon detection of
system voltage above V
all input signals are enabled immediately upon detection
of system voltage above V
registers at offsets 00h through 0Dh.
immediately upon detection of system voltage above
V
the battery voltage, V
V
drops below V
may be disabled and its functionality cannot be guaran-
teed.
and V
decreases the power consumption from the battery
connected to V
CMOS RAM is not affected as long as the battery is
present at a correct voltage level.
SBON
SB
BAT
SB
power supply is higher than V
is present or not.
power supply is higher than V
SB
.
Oscillator Activity
is removed. This disables the oscillator and
BATMIN
BAT
SB
. When disabling the oscillator, the
= 0), the lockout condition continues
. When this occurs, the oscillator
BAT
BAT
SBON
SBON
only), the battery voltage
.
. This also initializes
BATDCT
SBON
BATMIN
, independent of
and HMR is 1,
, regardless if
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