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2. RF Operation
Serial Communications
UART-Interfaced Data Flow
Serial Data
The WCM802 / WCM900 OEM RF Module interfaces to a host device through a CMOS-level
asynchronous serial port. Through its serial port, the module can communicate with any UART
voltage compatible device or through a level translator to any RS-232/485/422 device.
Devices that have a UART interface can connect directly through the pins of the WCM802 /
WCM900 Module as is shown in the figure below.
Figure 2.1. System Data Flow Diagram in a UART‐interfaced environment
(Low‐asserted signals distinguished with horizontal line over signal name.)
Data enters the prName Module through the DI pin (pin 4) as an asynchronous serial signal. The
signal should idle high when no data is being transmitted.
The UART performs tasks, such as timing and parity checking, that are needed for data
communications. Serial communication consists of two UARTs configured with compatible
parameters (baud rate, parity, start bits, stop bits, data bits) to have successful communication.
Each data packet consists of a start bit (low), 8 data bits (least significant bit first) and a stop bit
(high). The following figure illustrates the serial bit pattern of data passing through the module.
Figure 2.2. UART data packet 0x1F (decimal number "31") as transmitted through the WCM802 / WCM900
Module
Example Data Format is 8‐N‐1 (bits – parity ‐ # of stop bits)
20 JUN 2005
WCM802/900
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