PC87351 datasheet(51/86 Pages) NSC

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3.0 System Wake-Up Control (SWC)

3.1

OVERVIEW

The SWC wakes up the system by asserting the Power-Up Request (PWUREQ) output pin, in response to the following

maskable system events:

• Modem ring (RI1 and RI2 pins)

• Telephone ring (RING input pin)

• Any keyboard activity or speciﬁc programmable key sequence

• Any mouse activity or speciﬁc programmable click/s

• Two general-purpose events (PME1 and PME2 input pins).

This chapter describes the general SWC functional block. A device may include a different implementation. For the device

specific implementation, see the

Device Architecture chapter.

3.2

FUNCTIONAL DESCRIPTION

The SWC monitors seven system events or activities. Each one of them is fed into a dedicated detector that decides when

this event is active, according to predetermined (either fixed or programmable) criteria. A set of dedicated registers is used

to determine the wake-up criteria, including the Keyboard sequence.

A Wake-Up Events Status Register (WKSR) and a Wake-Up Events Control Register (WKCR) hold a Status bit and Enable

bit respectively, for each one of the events.

Upon detection of any active event, the corresponding Status bit is set to 1. If the event is enabled (the corresponding Enable

bit is set to 1), the PWUREQ output is asserted. In addition, detection of an active wake-up event may be also routed to any

arbitrary IRQ (or SMI over IRQ2 if Serial IRQ is used).

Disabling an event prevents it from issuing PWUREQ, but does not affect the Status bits. The PWUREQ signal is active

when both the Status and Enable bits equal 1 for at least one event.

The SWC logic is powered by VSB.

The SWC configuration registers are battery backed, powered by VPP. The setup of the wake-up events, including program-

mable sequences, is retained throughout power failures (no VSB) as long as the battery is connected. VPP is taken from VSB

when power is present; otherwise (power-fail), VBAT is used as the VPP source.

System reset does not affect these registers. They are reset only by software reset or power-up of VPP.

3.3

EVENT DETECTION

3.3.1

Modem Ring

High to low transitions on RI1 or RI2 indicate the detection of ring in external modem connected to Serial Port 1 or 2 respec-

tively and can be used as a wake-up event.

3.3.2

Telephone Ring

A telephone ring can be detected by the SWC by processing the raw signal coming directly from the telephone line into the

RING input pin. Detection of a pulse-train with a frequency higher than 16 Hz that lasts at least 0.3 sec is used as a wake-

up event.

The RING pulse-train detection is achieved by monitoring the falling edges on RING in time slots of 62.5 msec (a 16 Hz cycle).

A positive detection occurs if falling edges of RING are detected in three consecutive time slots, following a time slot in which

no RING falling edge is detected. This detection method guarantees the detection of a RING pulse-train with frequencies higher

than 16 Hz. It filters out (does not detect) pulses of less than 10 Hz, and may detect pulses between 10 Hz to 16 Hz.

3.3.3

Keyboard and Mouse Activity

The detection of either any activity or a specific predetermined Keyboard or Mouse activity can be used as a wake-up event.

The Keyboard wake-up detection can be programmed to detect:

• Any keystroke

• A speciﬁc programmable sequence of up to eight alphanumeric keystrokes

• Any programmable sequence of up to 8 bytes of data received from the keyboard.

The Mouse wake-up detection can be programmed to detect either any Mouse click or movement, or a specific programma-

ble click (left or right) or double-clicks.

3.3.4

General-Purpose Events

A general-purpose event is defined as the detection of falling edge, rising edge, low level, or high level on a specific signal.

Each signal’s event is configurable via software. PME1 and PME2 may wake up the system from power-off state, or generate

an interrupt if the system is in power-on state.

A debouncer of 16 ms is enabled (default) on each event. It may be disabled by software.

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