BC352239A Datasheet, PDF (65/116 Pages) List of Unclassifed Manufacturers – BlueCore 3-Multimedia External

8.5.1 UART Bypass
RXD
CTS
RTS
TXD
Host Processor
RESET
UART_TX
UART_RTS
UART_CTS
UART_RX
PIO4
PIO5
PIO6
PIO7
UART
Test Interface
BlueCore3-Multimedia
External
Device Terminal Descriptions
TX
RTS
CTS
RX
Another Device
Figure 8.22: UART Bypass Architecture
8.5.2 UART Configuration While RESET is Active
The UART interface for BlueCore3-Multimedia External while the chip is being held in reset is tri-state. This will
allow the user to daisy chain devices onto the physical UART bus. The constraint on this method is that any
devices connected to this bus must tri-state when BlueCore3-Multimedia External reset is de-asserted and the
firmware begins to run.
8.5.3 UART Bypass Mode
Alternatively, for devices that do not tri-state the UART bus, the UART bypass mode on
BlueCore3-Multimedia External can be used. The default state of BlueCore3-Multimedia External after reset is
de-asserted, this is for the host UART bus to be connected to the BlueCore3-Multimedia External UART, thereby
allowing communication to BlueCore3-Multimedia External via the UART.
In order to apply the UART bypass mode, a BCCMD command will be issued to BlueCore3-Multimedia External
upon this, it will switch the bypass to PIO[7:4] as shown in Figure 8.. Once the bypass mode has been invoked,
BlueCore3-Multimedia External will enter the deep sleep state indefinitely.
In order to re-establish communication with BlueCore3-Multimedia External, the chip must be reset so that the
default configuration takes affect.
It is important for the host to ensure a clean Bluetooth disconnection of any active links before the bypass mode
is invoked. Therefore it is not possible to have active Bluetooth links while operating the bypass mode.
8.5.4 Current Consumption in UART Bypass Mode
The current consumption for a device in UART Bypass Mode is equal to the values quoted for a device in
standby mode.
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