Specifications

32
6.1.1 UART Configuration While RESET is Active
The UART interface for WT32 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 a WT32 reset is de-
asserted and the firmware begins to run.
6.1.2 UART Bypass Mode
Alternatively, for devices that do not tri-state the UART bus, the UART bypass mode on
WT32 can be used. The default state of WT32 after reset is de-asserted, this is for the host
UART bus to be connected to the WT32 UART, thereby allowing communication to WT32
via the UART.
In order to apply the UART bypass mode, a BCCMD command will be issued to WT32.
Upon this, WT32 will switch the bypass to PIO[7:4] as shown in Figure 9. Once the bypass
mode has been invoked, WT32 will enter the deep sleep state indefinitely.
In order to re-establish communication with WT32, the chip must be reset so that the
default configuration takes effect.
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.
The current consumption for a device in UART Bypass Mode is equal to the values quoted
for a device in standby mode.
WT12
Host
processor
Test
interface
RXD
CTS
RTS
TXD
Another
device
TX
RTS
CTS
RX
UART_TX
UART_RTS
UART_CTS
UART_RX
RESET
PIO5
PIO6
PIO7
PIO4
UART
WTxx
Figure 9: UART bypass mode