ConnectWare Physical Layer

The ConnectWare Module supports four serial interfaces, however only one will be active at a time.

• RS-232

• RS-485

• USB 2.0 CDC Device Class

RS-232

The physical interface operates at standard RS-232 logic levels, not TTL levels. It supports TX, RX, and GND connections. The interface is full duplex. Implementations must support a minimum baud rate of 9600. 115200 is the preferred baud rate while rates of up to 230400 are supported. The port shall use no parity, 8 data bits, and 1 stop bit.

RS-485

The physical interface operates at standard RS-485 differential pair levels. It supports A, B, and GND connections. The interface is half duplex. Although RS-485 is multi-drop only one CWM and one OKE node may be connected to the bus simultaneously. Implementations must support a minimum baud rate of 9600. 115200 is the preferred baud rate while rates of up to 230400 are supported. The port shall use no parity, 8 data bits, and 1 stop bit.

The ConnectWare module has biasing resistors on the differential pair so that the lines will remain in an idle state when there are no devices actively transmitting on the bus. The OKE must implement terminating resistors as necessary to ensure reliable communication with the CWM.

USB 2.0 CDC Device Class

The USB 2.0 physical interface operates as a differential pair per the USB specification. It supports D+, D-, GND, and Vbus. Vbus should not be used by the OKE to power its internal electronics. The interface will support both Low-Speed and High-Speed USB modes. The CWM will be the USB host. Even though USB is multi-drop only 1 USB device, the OKE, may be connected to the bus. The host and device will communicate using the CDC device class, which provides a full duplex virtual serial port connection between the host and device. The actual baud rate setting is not relevant for USB, since it will either be transmitting data at Low-Speed or High-Speed depending on the device capabilities and startup USB handshaking.