STA2500D datasheet(34/57 Pages) STMICROELECTRONICS

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General specification

STA2500D

34/57

Doc ID 16067 Rev 1

Figure 9.

Wake-up by the Bluetooth controller with data transmission to the host,

through enhanced H4 SPI

Deep sleep mode entry and wake-up through H4 SPI

It requires BT_CLK_REQ_OUT_x (BT_CLK_REQ_OUT_1 for active high polarity and

BT_CLK_REQ_OUT_2 for active low polarity), BT_WAKEUP and BT_SPI_INT. The

BT_WAKEUP is used as wake-up signal from the Host, the BT_CLK_REQ_OUT_x requires

the clock from the Host and BT_SPI_INT is used as a wake-up signal from the Bluetooth

Controller.

●

Deep sleep mode entry

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

BT_WAKEUP of the STA2500D to ‘0’. 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 asserts

BT_CLK_REQ_OUT_x ‘inactive’ to tell the Host that it does not need the clock

anymore. The STA2500D cannot go in Deep Sleep mode by itself. Note that the Host

cannot force BT_WAKEUP to ‘0’ before the end of a write operation from the Host, this

in order to allow correct decoding of the message by the Bluetooth Controller.

●

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_WAKEUP pin of the STA2500D to ‘1’. Then the STA2500D asks

the Host to restart the system clock by setting BT_CLK_REQ_OUT_x to ‘active’. When

the clock is available and stable, the Host can use BT_SPI_CSN to start an SPI

transaction if needed (there is a programmable minimum delay between the assertion

of BT_CLK_REQ_OUT_x and the moment the Host can assert BT_SPI_CSN).

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

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

BT_CLK_REQ_OUT_x to ‘active’.

When the clock is available, the STA2500D sets BT_SPI_INT high to request the SPI

interface to the Host and waits for BT_SPI_CSN going low, indicating the SPI

transaction starts.

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

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

BT_CLK_REQ_OUT_x to ‘active’.

REF_CLK _IN

CLK _REQ_OUT_1

SPI_CLK

SPI_DI

SPI_DO

SPI_INT

SPI_CSN

DATA

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