XStream
‐
PKG
‐
T™
Telephone
RF
Modem
–
Product
Manual
v5.x00
[2006.02.24]
Header
The header contains network addressing information that is used to filter incoming RF data. The
receiving modem checks for matching a VID, Hopping Channel and Destination Address. Data
that does not pass through all three network filter layers is discarded.
Figure
2
‐
04.
Filtration
Layers
Contained
in
the
Header
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 modem computes the CRC on all incoming RF data. Received data
that has an invalid CRC is discarded [Refer to Receive Mode section].
2.1.3.
Receive Mode
If a modem detects RF data while operating in Idle Mode, the modem transitions into Receive
Mode to start receiving RF packets.
Figure
2
‐
05.
Reception
of
RF
Data
Æ
After a packet is received, the
modem 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 modem returns to Idle Mode
after 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 modem is in
Receive Mode, the serial data will
be transmitted after the modem
is finished receiving data and
returns to Idle Mode.
©
2006
MaxStream,
Inc.,
Confidential
and
Proprietary
11
