STA2500DTR STMICROELECTRONICS [STMicroelectronics], STA2500DTR Datasheet - Page 31

• Manufacturer Part Number: STA2500DTR
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

STA2500D
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.
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'.
Doc ID 16067 Rev 1
General specification
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