STA2500D Datasheet, PDF (30/57 Pages) STMicroelectronics – Bluetooth™ V2.1 + EDR ("Lisbon") for automotive applications

General specification
STA2500D
6.10.2
6.10.3
Some examples for the usage of the low power modes
Sniff or sniff subrating
The STA2500D is in active mode with a Bluetooth connection. Once the transmission is
concluded, Sniff or Sniff Subrating is programmed. When one of these two states is entered,
the STA2500D goes into Sleep mode. After that, the Host may decide to place the
STA2500D in Deep Sleep mode as described in Section 6.10.3. The Deep Sleep mode
allows for lower power consumption. When the STA2500D needs to send or receive a
packet (e.g. at T_sniff or at the beacon instant), the STA2500D requests the system clock and
enters active mode for the needed transmission/reception. Immediately afterwards, the
STA2500D will go back to Deep Sleep mode. If some HCI transmission is needed, the
UART/SPI link will be reactivated, using one of the four ways explained in Section 6.10.3
and the STA2500D will move from Deep Sleep mode to Sleep mode.
Inquiry/page scan
When only Inquiry scan or Page scan is enabled, the STA2500D will go in Sleep mode or
Deep Sleep mode outside the receiver activity. The selection between Sleep mode and
Deep Sleep mode depends on the UART/SPI activity as in Sniff or Sniff Subrating.
No connection
If the Host allows Deep Sleep mode (as described in Section 6.10.3) and there is no activity,
then the STA2500D puts itself in Deep Sleep mode. It is possible to exit the Deep Sleep
mode by using one of the four methods explained in Section 6.10.3. In this Deep Sleep
mode (no connection), the Host can also decide to put the STA2500D in Complete Power
Down to further reduce the power consumption. In this case some part of the STA2500D will
be completely powered off. The request to quit the Complete Power Down is done either by
putting the BT_WAKEUP signal to ‘1’ or with an HW reset.
Active link
When there is an active link ((e)SCO or ACL), the Bluetooth Controller will not go in Deep
Sleep mode and not in Complete Power Down. But the Bluetooth Controller is made in such
a way that whenever it is possible, depending on the scheduled activity (number of link, type
of link, amount of data exchanged), it goes in Sleep mode.
Deep sleep mode entry and wake-up
During periods of no activity on the Bluetooth and on the Host side, the chip can be placed
in Deep Sleep mode. Four ways to initiate Deep Sleep mode and to wake up are supported
(selection is done through software parameter download): they are respectively based on a
UART interface in the first case, an SPI interface in the second case and third case, while
either UART or SPI interfaces can be used in the fourth case that is based on an handshake
mechanism.
Deep sleep mode entry and wake up through H4 UART
It requires BT_CLK_REQ_OUT_1, BT_UART_RXD and BT_UART_RTS. The
BT_UART_RXD is used as wake-up signal from the Host, the BT_CLK_REQ_OUT_1
requires the clock from the Host and the BT_UART_RTS indicates when the STA2500D is
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Doc ID 16067 Rev 1