STLC2500ATR datasheet(25/37 Pages) STMICROELECTRONICS

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STLC2500A

General specification

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Figure 5.

Low power modes [Initiated deep sleep, mode 1]

[Initiated Deep Sleep, mode 2]

In this mode, the clock request and the host wake-up signalling have been decoupled.

These functions are now covered by 2 independant signals: the HOST_WAKEUP pin

only covers the clock request functionality, GPIO3 is used as a wakeup signal to the

Host.

This mode uses the following signals: HOST_WAKEUP (only used as a clock request

signal), BT_WAKEUP and GPIO3 (used as host wakeup signal). UART_RTS,

UART_CTS are only used to stop/allow UART activity.

–

The Host wakeup procedure

A Bluetooth Controller initiated wakeup of the Host is always initiated by GPIO3.

GPIO3 signals whether the Bluetooth Controller needs the Hosts attention: only if

there are data or HCI events to be sent over the UART interface, the Bluetooth

Controller will assert GPIO3 (requesting the Hosts attention).

When the Host sees a high level on GPIO3, it must wakeup (when asleep) and

assert the UART_CTS signal, allowing the Bluetooth Controller to send data or

HCI events. When asserting GPIO3, the Bluetooth Controller will make sure the

UART is open and that the UART_RTS signal is asserted.

Note that the UART will be closed (and the UART_RTS will be deasserted) by the

Bluetooth Controller when BT_WAKEUP is low and there is no data to be sent to

the Host. In that case, GPIO3 will also be low.

–

The wakeup/fall-asleep procedures for the Bluetooth Controller.

The wakeup/fall-asleep procedures for the Bluetooth Controller are always

initiated by the HOST_WAKEUP (i.e.clock request) or BT_WAKEUP signal.

–

The system goes into low power as follows:

the Host sets BT_WAKEUP to '0', telling the Bluetooth Controller that it can go in

low power. The Bluetooth Controller decides to enter low power mode or not,

depending on its scheduled activity and on the number of events or data packets

to be sent to the Host. When it decides to enter low power mode (meaning that

there is no scheduled activity and that there are no data or HCI events to be sent -

Active

Sleep Mode

Deep Sleep

Mode

Complete Power Down

Host: BT_WAKEUP=‘1’

Hard Reset

UART off

Host: BT_WAKEUP=‘0’=UART_RXD

AND

BT Controller: HOST_WAKEUP=‘0’

and UART_RTS=‘1’

UART on

Host: sends a specific HCI command.

Host: BT_WAKEUP=‘1’=UART_RXD

BT Controller: HOST_WAKEUP=‘1’

(UART_RTS=‘0’)