User's Manual

MaxStream 9XStream™ Wireless OEM Module Manual v2.8
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Confidential and Proprietary, ©MaxStream, Inc. 2001
Cyclic Sleep (SM=3-7)
If the Cyclic Sleep setting is enabled, the 9XStream module goes into Sleep
Mode after a user-defined period of inactivity (no transmission or reception on
the RF channel). The user-defined period may be set by adjusting the ST
parameter (see the ST command in the 9XStream Commands Table –
Appendix E).
The module remains in Sleep Mode for a user-defined period of time ranging
from 0.5 seconds to 8 seconds (adjustable using SM command). After this
period of time, the module returns to Idle Mode and listens for a valid data
packet. If no valid data packet is found (on any channel), the module returns to
Sleep Mode. If a data packet is found, the module transitions into Receive
Mode and receives the incoming packets until another ST inactivity time out
occurs. When the module is awake, it requires 100 milliseconds to search for a
valid data packet.
While the module is in a low-power state, the CTS pin (Pin 1) is de-asserted
(high) to indicate that data should not be sent to the module during this time.
When the module awakens to listen for data, the CTS pin is asserted, and any
data received on the DI pin will be transmitted. The TX/PWR pin (Pin 8) is also
de-asserted (low) when the module is in Cyclic Sleep Mode. It is asserted each
time the module cycles into Idle Mode to listen for valid data packets, and then
de-asserts if the module returns to Sleep Mode.
Cyclic Scanning
Each RF packet consists of a header and data as shown previously in Figure 5a.
Since the header contains the channel synchronization information, the module
must wake up during the header portion of a packet in order to synchronize with
the transmitter and receive the data. To ensure that the 9XStream module can
detect the header, a long header can be sent periodically during a transmission.
This long header repeats the synchronization information for a period of time
defined by the LH command.
By default, the long header is turned off and must be enabled in order to
communicate with a module operating in Cyclic Sleep Mode. To enable the
long header, the LH parameter must be set to a value greater than the time of
cyclic sleep to ensure accurate detection by the receiver(s). For example, if the
9XStream is set to wake up from Sleep Mode every four seconds and check for
a packet, a transmitter would need to send a long header that is just over four
seconds in length to guarantee that the receiving module will detect the packet.
(Exact timing requirements can be found in the Timing Diagrams section.)
This concept of long header length versus Sleep Mode timing is displayed in
Figure 7a and b.