Product manual

XStream‐PKG‐R™RS‐232/485RFModem–ProductManualv4.2B
©2005MaxStream,Inc.Confidential&Proprietary   14
3.2. Modes of Operation
XStream RF Modems operate in five modes.
Figure3.3. XStreamModesofOperation
Modemcanonlybeinonemodeatatime.
3.2.1. Idle Mode
When not receiving or transmitting data, the modem is in Idle Mode. The modem uses the same
amount of power in Idle Mode as it does in Receive Mode.
The modem shifts into the other modes of operation under the following conditions:
• Serial data is received in the DI Buffer (Transmit Mode)
• Valid RF data is received through the antenna (Receive Mode)
• Command Mode Sequence is issued (Command Mode)
• Sleep Mode condition is met (Sleep Mode)
After responding to any of the preceding conditions, the modem automatically transitions back
into Idle Mode.
3.2.2. 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3.4. TransmissionofDataÆ
Once in Transmit Mode, the modem
initializes a communications channel.
Channel initialization is the process o
sending an RF initializer that
synchronizes receiving modems with
the transmitting modem. When
streaming multiple RF packets, the
RF Initializer is only sent in front of
the first packet. During channel
initialization, incoming serial data
accumulates in the DI buffer.
f
kets
nd
nues
n
After the channel is initialized, data in
the DI buffer is grouped into pac
(up to 64 bytes in each packet) a
is transmitted. The modem conti
to transmit data packets until the DI
buffer is empty. Once transmission is finished, the modem returns to Idle Mode. This progressio
is shown in Figure 3.4.
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.