Specifications

31
The UART interface is capable of resetting WT32 upon reception of a break signal. A Break
is identified by a continuous logic low (0V) on the UART_RX terminal, as shown in Figure
8. If tBRK is longer than the value, defined by the PS Key
PSKEY_HOST_IO_UART_RESET_TIMEOUT, (0x1a4), a reset will occur. This feature allows
a host to initialize the system to a known state. Also, WT32 can emit a Break character
that may be used to wake the Host.
Since UART_RX terminal includes a weak internal pull-down, it cannot be left open unless
disabling UART interface using PS_KEY settings. If UART is not disabled, a pull-up resistor
has to be connected to UART_RX. The UART interface requires an external RS232
transceiver, which usually includes the required pull-up.
t
BRK
UART_RX
Figure 8: Break signal
Table 11 shows a list of commonly used Baud rates and their associated values for the
Persistent Store Key PSKEY_UART_BAUDRATE (0x204). There is no requirement to use
these standard values. Any Baud rate within the supported range can be set in the
Persistent Store Key according to the formula in Equation below.
Baud Rate =
PSKEY_UART_BAUD_RATE
0.004096
Equation 2: Baud rate calculation formula
Hex Dec
1200 0x0005 5 1.73%
2400 0x000a 10 1.73%
4800 0x0014 20 1.73%
9600 0x0027 39 -0.82%
19200 0x004f 79 0.45%
38400 0x009d 157 -0.18%
57600 0x00ec 263 0.03%
76800 0x013b 315 0.14%
115200 0x01d8 472 0.03%
230400 0x03b0 944 0.03%
460800 0x075f 1887 -0.02%
921600 0x0ebf 3775 0.00%
1382400 0x161e 5662 -0.01%
1843200 0x1d7e 7550 0.00%
2765800 0x2c3d 11325 0.00%
Persistent store values
Baud rate Error
Table 11: UART baud rates and error values