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7. Functional Description

The Wireless LAN module is a self-contained product and requires only power to implement full

communication. The integrated, high performance antenna together with the RF and baseband circuitry

provides the Wireless LAN connectivity and the UART interface for a connection to a host system.

The complexity and flexibility of configuration are made simple for the design engineer by the

integration of an extremely comprehensive scripting language - UWScript. UWScript provides a simple

BASIC style language with a rich library of built-in functions that simplify connection of the module.

7.1 Interfaces

7.1.1 UART interface

Modem signal nomenclature can be a source of great confusion, particularly on devices which can be

configured in either DCE (Data Communications Equipment) or DTE (Data Terminal Equipment) format.

For the purpose of this data sheet all UART signals are defined on the assumption that the module is

being used as a conventional DCE. I.e it is behaving like a serial PSTN modem.

/TXD, /RXD, /RTS and /CTS form a conventional asynchronous serial data port with handshaking,

conforming to the ITU-T v.24 standard for DCE signalling. The interface is designed to operate correctly

when connected to other UART devices such as a 16550A. Note that the signalling levels are a nominal

0V and 3.0V and are inverted with respect to the signalling on an RS232 cable. The interface is

programmable over a variety of baud rates, with no, even or odd parity, one or two stop bits and

hardware flow control. Non-standard baud rates are supported – for more information please contact

EZURiO. Auto-bauding is not supported.

On power-up the UART defaults to 115200,n,8,1.

Note that there is no standardisation regarding the nomenclature of RX and TX across a DCE-DTE

interface. Some implementations show TX(DCE) connected to TX(DTE) to give naming consistency

across a cable, whereas other show TX driving RX to reflect logical port directions. Always check the

direction of ports on DCE and DTE.

In a DCE mode, where the module is being driven as a peripheral by a host processor application, the

UART signals should be connected according to the following scheme:

Port /RXD of the WISM transmits data to the application’s /RXD input.

Port /TXD of the WISM receives data from the application’s /TXD output.

Two-way hardware flow control is implemented by /RTS and /CTS. In DCE mode, /RTS is an OUTPUT

and is active low. /CTS is an INPUT and is active low. These signals operate according to normal

industry convention.

Some serial implementations link /CTS and /RTS to remove the need for handshaking. EZURiO does

not recommend linking /CTS and /RTS other than for testing and prototyping. If these pins are linked

and the host sends data at the point that the Wireless Module deasserts its /RTS signal, then there is a

significant risk that internal receive buffers will overflow which could lead to a loss of data. EZURiO

recommend that the correct /CTS to /RTS handshaking protocol be adhered to in order to ensure

proper operation.

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