STA2500D datasheet(31/57 Pages) STMICROELECTRONICS

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STA2500D

General specification

Doc ID 16067 Rev 1

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available. In this mode, the break function (BT_UART_RXD is low for more than 1 word) is

used to distinguish between normal operation and low power mode usage.

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Deep sleep mode entry

The Host tells the STA2500D that it can go in Deep Sleep mode power by forcing the

BT_UART_RXD of the STA2500D to '0' for more than 1 word. The STA2500D decides

to go in Deep Sleep mode, or not, depending on its scheduled activity and on the

number of events or data packets to be sent to the Host. In case it decides to go in

Deep Sleep mode, it signals it by forcing BT_UART_RTS high; then it asserts

BT_CLK_REQ_OUT_1 low to tell the Host that it does not need the clock anymore. The

STA2500D cannot go in Deep Sleep mode by itself. This is a logical consequence of

the fact that the system clock is needed to receive characters on the UART.

Note that when the system is in Deep Sleep mode, the UART is closed.

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Deep sleep mode wake-up

The wake-up procedure can be initiated by the Host or by the STA2500D. In the latter

case, it can be with or without communication, depending if there are data to be

transmitted to the Host.

Wake-up initiated by the Host

The Host sets the BT_UART_RXD pin of the STA2500D to '1'. Then the STA2500D

asks the Host to restart the system clock by setting BT_CLK_REQ_OUT_1 to '1'. When

the clock is available, the STA2500D confirms it is awake by releasing BT_UART_RTS

to '0'.

Autonomous wake-up with UART communication (i.e. initiated by the STA2500D)

The STA2500D first asks the Host to restart the system clock by setting

BT_CLK_REQ_OUT_1 to '1'.

When the clock is available, the STA2500D sets BT_UART_RTS low, and then the Host

can give confirmation by releasing the BT_UART_RXD of the STA2500D.

Another possibility is that the STA2500D sets BT_HOST_WAKEUP to ‘1’ to request the

Host attention. Then the Host can give confirmation by releasing the BT_UART_RXD of

the STA2500D and the STA2500D sets BT_UART_RTS low.

The choice between the two possibilities is selected by a software parameter.

Autonomous wake-up without UART communication (i.e. initiated by the STA2500D)

The STA2500D asks the Host to restart the system clock by setting

BT_CLK_REQ_OUT_1 to '1'.

STA2500D Datasheet(PDF) 31 Page - STMicroelectronics