PC87307 datasheet(55/218 Pages) NSC

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Real-Time Clock (RTC) and Advanced Power Control (APC) (Logical Device 2)

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Bit 7 - Interrupt Request Flag (IRQF)

This read-only bit is the inverse of the value on the IRQ

output signal of the RTC/APC.

0 - IRQ is inactive (high).

1 - IRQ is active (low) and any of the following condi-

tions exists: both PIE and PF are 1; both AIE and

AF are 1; both UIE and UF are 1. (PIE, AIE and

UIE are bits 6, 5 and 4, respectively of the CRB

4.2.4

RTC Control Register D (CRD), Index 0Dh

This register indicates the validity of the RTC RAM data.

FIGURE 4-8. CRD Bitmap

Bits 6-0 - Reserved

These bits are reserved and are always 0.

Bit 7 - Valid RAM and Time (VRT)

The VRT bit senses the voltage that feeds this logical

device (VCCH or VBAT) and indicates whether or not it

was too low since the last time this bit was read. If it was

too low, the RTC and RAM data are not valid.

This read-only bit is set to 1 when this register is read.

0 - The voltage that feeds the APC/RTC logical device

was too low.

1 - The RTC and RAM data are valid.

WARNING:

If VCCH ramps down at a rate exceeding 1 V/msec, it

may reset this bit.

VRT

76543210

Reserved

Index 0Dh

Power-Up

Required

RTC Control

(CRD)

Reset

4.3

APC OVERVIEW

Advanced Power Supply Control (APC) is implemented

within the RTC logical device. It enables the PC to power up

automatically, as required by specific conditions, or to pow-

er down in an orderly, controlled manner, replacing the

physical power supply On/Off switch.

The APC device is powered at all times that external AC

power or battery backup power are connected to the RTC

device. This is true even though the PC may be switched off

or disconnected from the external AC power outlet, in which

case the APC device is active but does not activate system

power. The APC device powers up the entire PC system

upon the occurrence of various events (including the power-

on switch event).

WARNING:

The APC device does not function if the 32.768 KHz os-

cillator is not running.

The APC function produces the ONCTL signal to activate

the system power supply, and the Power-Off Request

(POR) interrupt request signal when there is a request for

power off.

ONCTL: The ONCTL signal physically activates or deacti-

vates the system power supply.

The ONCTL value depends on the following:

• External events

• Programmable parameter settings

• The system state when an external event occurs

• The state of the system power supply.

POR: The APC generates a Power-Off Request (POR) in-

terrupt request signal when the power switch is manually

toggled to turn the power off. This enables a software con-

trolled exit procedure (analogous to the autoexec.bat

startup procedure in DOS operating systems) with automat-

ic activation of preprogrammed features such as system

status backup, system activity logging, file closing and

backup, remote communications termination, print comple-

tion, etc.

Table 4-4 shows the registers used for Automatic Power

Supply Control (APC) in the part.

TABLE 4-4. APC Control Register List

4.3.1

User Selectable Parameters

The APC function enables users to tailor system response

to power up, power down, power failure and battery opera-

tion situations.

User-selectable parameters include:

• Enabling various external events to wake up the sys-

tem. See “Power Up” on page 58.

• Wake-up time for an automatic system wake-up. See

“Predetermined Wake-Up” on page 60.

Index

Mnemonic

Description

40h

APCR1

APC Control Register 1

41h

APCR2

APC Control Register 2

42h

APSR

APC Status Register

47h

RLR

RAM Lock Register

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