User's Manual

MaxStream 9XStream™ Wireless OEM Module Manual v2.8

Confidential and Proprietary, ©MaxStream, Inc. 2001

DI (Data In) – Pin 4 (Input)

Data enters the 9XStream on the DI pin as an asynchronous serial signal. The

serial signal is idle (high) when no data is being transmitted. Each data packet

consists of a start bit (low), 8 data bits, and a stop bit (high) as shown below in

Figure 3.

Figure 3

The 9XStream modules transfer exactly 8-bits over the air. The start and stop

bits from the UART signal are not actually transmitted, but are regenerated on

the receiving module before they are sent out the serial port. This allows for

the following data configurations to be sent:

• 8-bit, no parity, 1 stop bit

• 7-bit, even parity, 1 stop bit

• 7-bit, odd parity, 1 stop bit

• 7-bit, no parity, 2 stop bits

Since the 9XStream is half-duplex, it can only transmit or receive at a given

time. Thus, once the first byte is detected on the DI pin, the 9XStream

immediately begins transmitting the incoming data unless over-the-air data is

already being received. In this case, the data on the DI pin is stored in the data

buffer until data is no longer being received at the antenna.

If the 9XStream

receives a lengthy sequence of serial data (while receiving over-the-air

data), the data buffer could reach its capacity

(132 bytes) in which case the

CTS signal will need to be implemented (see CTS section below).

Note: The 9600 and 19200-baud modules allow incoming serial data

to be transferred at a rate of 2400-57600 bits/second. Serial

data can be transferred to the module at a rate equal to or

less than the module’s over-the-air baud rate without any

problems. However, if the serial interface rate is set to

exceed the module’s baud rate (9600 or 19200 bps

respectively), CTS must be implemented since the data

buffer may become full.