Data Sheet

Doc No: WG7833-B0-DTS-R06

http://www.jorjin.com.tw

CONFIDENTIAL

Page 31

5.3. HCI UART Shared Transport Layers for All Functional Blocks

The HCI UART supports most baud rates (including all PC rates) for all fast clock frequencies

up to a maximum of 4 Mbps. After power up the baud rate is set for 115.2 kbps, regardless of

fast clock frequency. The baud rate can then be changed by using a VS command. The Device

responds with a Command Complete Event (still at 115.2 kbps), after which the baud rate

change occurs.

HCI hardware includes the following features:

 Receiver detection of break, idle, framing, FIFO overflow and parity error conditions.

 Receiver Transmitter underflow detection.

 CTS/RTS hardware flow control.

 4 wires (H4)

The below table lists the UART default settings

Table 5-3. UART Default Setting

Parameter

Value

Bit Rate

115.2 kbps

Data Length

8 bits

Stop Bit

Parity

None

5.3.1. UART 4-Wires Interface – H4

The interface includes four signals: TXD, RXD, CTS and RTS. Flow control between the host

and the Device is byte-wise by hardware. ( See Figure 5-5 )

Figure 5-5. HCI UART Connection

When the UART RX buffer of the device passes the flow-control threshold, the buffer sets the

UART_RTS signal high to stop transmission from the host. When the UART_CTS signal is set

high, the device stops transmitting on the interface. If HCI_CTS is set high in the middle of

transmitting a byte, the device finishes transmitting the byte and stops the transmission.