PC87307VUL National Semiconductor, PC87307VUL Datasheet - Page 56

• Manufacturer Part Number: PC87307VUL
• Description: PC87307/PC97307 Plug and Play Compatible and PC97 Compliant SuperI/O
• Manufacturer: National Semiconductor

www.national.com
4.3.2
The system power state may be No Power, Power On, Pow-
er Off or Power Failure. These states are illustrated in Fig-
ure 4-9 on page 57. Table 4-5 indicates the power-source
combinations for each state. No other power-source combi-
nations are valid.
In addition, the power sources and distribution for the entire
PC system are described in “PC87307/PC97307 Power
Supplies” on page 51.
WARNING:
No Power
This state exists when no external or battery power is con-
nected to the device. This condition will not occur once a
backup battery has been connected, except in the case of a
malfunction. The APC undergoes initialization only when
leaving this state.
Power On
This is the normal state when the PC 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 PC
power supply is powered by external AC power and produc-
es V
by V
is powered by V
•
•
•
V
Type of system recovery after a Power Failure state
by setting the MOAP bit. See page “The MOAP Bit” on
page 58.
Immediate or delayed Switch Off shutdown. See “The
SWITCH Input Signal” on page 59.
5 or 21 second time-out fail-safe shutdown. See “The
SWITCH Input Signal” on page 59.
It is illegal for V
+
+
DD
DD
DD,
and V
with the exception of the RTC logical device, which
System Power States
TABLE 4-5. System Power States
CCH
V
CCH
+
CCH.
. The PC system and the part are powered
DD
Real-Time Clock (RTC) and Advanced Power Control (APC) (Logical Device 2)
to be present when V
+ or -
+ or -
V
BAT
+
+
Power Failure
Power State
Illegal State
No Power
Power Off
Power On
CCH
is absent.
56
Power Off (Suspended)
This is the normal state when the PC has been switched off
and is not required to be active, but is still connected to a
live external AC input power source. This state may be ini-
tiated directly or by software. The PC system is powered
down. The RTC logical device remains active, powered by
V
Power Failure
This state occurs when the external power source to the PC
stops supplying power, due to disconnection or power fail-
ure on the external AC input power source. The RTC con-
tinues to maintain timekeeping and RAM data under battery
power (V
RTC. In this case, the oscillator stops functioning if the sys-
tem goes to battery power, and timekeeping data becomes
invalid.
4.3.3
In the Power On state, the PC host is powered by the pow-
er-supply voltage V
the Power Off state, if the conditions for this state occur
(See Section 4.4.3), or the Power Failure state if external
power is removed.
In the Power Off state, the PC hosts do not receive power
from the system power supply, except for RTC and APC
which receive V
state if the conditions for this state occur (see Section
4.4.3), or enter the Power Failure state if external power is
removed.
If the system voltage falls to the level of V
less, the APC enters the Power Failure state and switches
to battery power.
When power returns after a power failure, the APC enables
power up after a delay of 1 second. The nature of the power
up depends on the MOAP bit setting (See “The MOAP Bit”
on page 58).
Knowing the system power state prior to a switch interrupt
is required for correct Switch Event interpretation. The pow-
er state is defined by the following conditions:
V
V
If V
timekeeping functions and the APC, all stop functioning.
If no external or battery-backup power is available, the sys-
tem enters a No Power state. Upon leaving this state, the
system is initialized.
CCH
DD
CCH
BAT
present implies Power On
.
present and V
falls below 2V with V
System Power Switching Logic
BAT
), unless the oscillator stop bit was set in the
CCH.
DD
DD
The system may enter the Power On
. From this state the system enters
absent implies Power Off.
CCH
absent, the oscillator, the
BAT
+500 mvolt or