XStream
‐
PKG
‐
T™
Telephone
RF
Modem
–
Product
Manual
v5.x00
[2006.02.24]
2.1.2.
Transmit Mode
When the first byte of serial data is received from the UART in the DI buffer, the modem
attempts to shift to Transmit Mode and initiate an RF connection with other modems.
Figure
2
‐
02.
Transmission
of
Dat
nsmit
a
Once in Tra
Mode, the
nnel.
s
s,
on,
buffer.
p to 64
e
modem initializes a
communications cha
Channel initialization is the
process of sending an RF
initializer that synchronize
receiving modems with the
transmitting modem. When
streaming multiple RF packet
the RF Initializer is only sent in
front of the first packet.
During channel initializati
incoming serial data
accumulates in the DI
After the channel is initialized,
data in the DI buffer is
grouped into packets (u
bytes in each packet) and is transmitted. The modem continues to transmit data packets until th
DI buffer is empty. Once transmission is finished, the modem returns to Idle Mode. This
progression is shown above.
As the transmitting modem nears the end of the transmission, it inspects the DI buffer to see if
more data exists to be transmitted. This could be the case if more bytes arrived from the host
after the transmission began. If more data is pending, the transmitting modem assembles a
subsequent packet for transmission.
RF Packet
The RF packet is the sequence of data used for communicating information between MaxStream
Modems. An RF Packet consists of an RF Initializer and RF Data.
©
2006
MaxStream,
Inc.,
Confidential
and
Proprietary
10
Figure
2
‐
03.
RF
Packet
Components
*
When
streaming
multiple
RF
packets,
the
RF
Initializer
is
only
sent
in
front
of
the
first
packet.
RF Initializer
An RF initializer is sent each time a new connection sequence begins. The RF initializer contains
channel information that notifies receiving modems of information such as the hopping pattern
used by the transmitting modem. The first transmission always sends an RF initializer.
An RF initializer can be of various lengths depending on the amount of time determined to be
required to prepare a receiving modem. For example, a wake-up initializer is a type of RF
initializer used to wake remote modems 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 modems are in cyclic sleep.
