General specification

STLC2500A

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6.7.4

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.

6.8

Initiated deep sleep modes

During periods of no activity on the Bluetooth and on the Host side, the chip can be placed

in Deep Sleep Mode. Two modes to initiate deep sleep mode and to wake up are supported

(selection is done through pin configuration, see

Table 14):

1.

[Initiated Deep Sleep, mode 1]

It requires HOST_WAKEUP, UART_RXD (connected with BT_WAKEUP, the two paths

will be physically connected on the board) and UART_RTS. The UART_RXD is used as

wakeup signal from the host, the HOST_WAKEUP requires the clock from the Host and

the UART_RTS indicates when the Bluetooth Controller is available. In this mode, the

break function (UART_RXD is low for more than 1 word) is used to distinguish between

normal operation and low power mode usage.

–

The system goes in low power mode in this way:

the Host tells the Bluetooth Controller that it can go in low power by forcing the

UART_RXD of the Bluetooth Controller to '0' for more than 1 word. The Bluetooth

Controller decides to go in low power mode, or not, depending on its scheduled

activity. In case it decides to go in low power mode, it signals it by forcing

UART_RTS high; then it asserts HOST_WAKEUP low to tell the Host that it does

not need the clock anymore. The Bluetooth Controller 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 and only the Host can stop the UART

link.

–

The system wakes up in this way:

the Bluetooth Controller first asks the Host to restart the system clock by setting

HOST_WAKEUP to '1'. When the clock is available, the Bluetooth Controller sets

UART_RTS low, and then the Host can give confirmation by releasing the

UART_RXD of the Bluetooth Controller. In case the Host wants to wake up the

Bluetooth Controller, it sets the UART_RXD pin of the Bluetooth Controller to '1'.

The Bluetooth Controller confirms it is awake by releasing UART_RTS to '0'.