SENA Parani-BCD100 - Manual (Page 12)

PARANI-BCD100
Page 12 of 22
4. Device Terminal Descriptions
4.1 UART Interface
UART (Universal Asynchronous Receiver and Transmitter) interface provides a simple mechanism for
communicating with other serial device using the RS232 protocol. When BCD100 is connected to another
digital device, UART_RX and UART_TX transfer data between the two devices. The remaining two signals,
UART_CTS, UART_RTS, can be used to implement RS232 hardware flow control where both are active low
indicators. All UART connections are implemented using CMOS technology and have signaling levels of 0V
and 3.3V
Parameter Possible Values
Baud Rate Minimum 1200 baud (2%Error)
Maximum 3M baud (1%Error)
Flow Control RTS/CTS or None
Parity None, Odd or Even
Number of Stop Bits 1 or 2
Bits per Channel 8
Table 4-1 Possible UART Settings
4.2 USB Interface
BCD100 USB devices contain a full speed (12Mbits/s) USB interface that is capable of driving of a USB
cable directly. No external USB transceiver is required. The device operates as a USB peripheral,
responding to requests from a master host controller such as a PC. Both the OHCI and the UHCI standards
are supported. The set of USB endpoints implemented behave as specified in the USB section of the
Bluetooth specification v2.0+EDR or alternatively can appear as a set of endpoints appropriate to USB audio
devices such as speakers. As USB is a Master/Slave oriented system (in common with other USB
peripherals), BCD100 only supports USB slave operation.
The USB data lines emerge as pins USB_DP and USB_DN. These terminals are connected to the internal
USB I/O buffers of the BCD100, therefore, have low output impedance. To match the connection to the
characteristic of the USB cable, resistors must be placed in series with USB_DP/USB_DN and the cable.
BCD100 features an internal USB pull-up resistor. This pulls the USB_DP pin weakly high when BCD100 is
ready to enumerate. It signals to the PC that it is a full speed (12Mbit/s) USB device.
The USB internal pull-up is implemented as a current source, and is compliant with section 7.1.5 of the USB
specification v1.2. The internal pull-up pulls USB_DP high to at least 2.8V when loaded with a 15KΩ±5%
pull-down resistor (in the hub/host) when VDD_PADS=3.1V. This presents a Thevenin resistance to the host
of at least 900Ω.