Receive Mode; Shutdown Mode - Digi XTend User Manual

An RF initializer can be of various lengths depending on the amount of time determined to be required to prepare a
receiving module. For example, a wake-up initializer is a type of RF initializer used to wake remote modules from
Sleep Mode (Refer to the FH, LH, HT and SM Commands for more information). The length of the wake-up initializer
should be longer than the length of time remote modules are in cyclic sleep.
Header
The header contains network addressing information that filters incoming RF data. The receiving module checks for
matching a Hopping Channel, VID and Destination Address. Data that does not pass through all three network filter
layers is discarded.
Refer to the
CRC (Cyclic Redundancy Check)
To verify data integrity and provide built-in error checking, a 16-bit CRC (Cyclic Redundancy Check) is computed for
the transmitted data and attached to the end of each RF packet. On the receiving end, the receiving module
computes the CRC on all incoming RF data. Received data that has an invalid CRC is discarded.

Receive mode

If a module detects RF data while operating in Idle Mode, the module transitions to Receive Mode to start receiving RF
packets. Once a packet is received, the module checks the CRC (cyclic redundancy check) to ensure that the data was
transmitted without error. If the CRC data bits on the incoming packet are invalid, the packet is discarded. If the CRC
is valid, the packet proceeds to the DO Buffer.
The module returns to Idle Mode when valid RF data is no longer detected or after an error is detected in the received
RF data. If serial data is stored in the DI buffer while the module is in Receive Mode, the serial data will be transmitted
after the module is finished receiving data and returns to Idle Mode.

Shutdown mode

Hardware Sleep
For applications where power consumption must be kept to a minimum during idle periods, Shutdown Mode offers
the lowest power mode available to the module.
When the SHDN pin (pin 7) is driven low, the module is forced into shutdown mode. Any communication in progress
(transmit or receive) will be halted and any buffered data will be lost. For any other mode of operation, SHDN must be
driven or pulled high. While in shutdown mode, the module's VCC pin draws 5 µA (typical).
Immediately after the SHDN pin changes state from low to high, the module resets. After reset, there is a delay that
must be observed. Delay time is <100ms.
While SHDN pin is driven low, the following pins are set to high impedance by the module: DCD, TX_PWR, RX LED, DO
and CTS (See pin signal descriptions, p6). The SHDN line (also used for RSSI indication) is driven low during shutdown.
The following input pins may continue to be driven by external circuitry when in shutdown mode: PIN_PWR_DWN,
RTS, DI and SHDN.
Note Because the DO pin also goes high impedance, if the XTend RF Module is connected to a processor, the UART
receive pin could be floating. A weak pull-up should be placed between the module and the microcontroller
so that data is not interpreted as being transmitted to the microprocessor.
XTend RF Module User Guide
Addressing on page 65 for more information.
Modes of operation
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