Murata Electronics North America 910M Manual Do Utilizador
WIT910
2.3.3. Low Power Mode and Duty Cycling
To conserve power, WIT910 remotes power down the receiver and transmitter between
hops when not in use. Base stations must remain active all the time to handle any
transmission from any remote. Remotes can save even more power by enabling the duty
cycle feature. This feature causes a remote to power down for 2
hops when not in use. Base stations must remain active all the time to handle any
transmission from any remote. Remotes can save even more power by enabling the duty
cycle feature. This feature causes a remote to power down for 2
N
frequency hops where
1/2
N
is the duty cycle. Rather than attempting to transmit on every frequency hop when
data is in the transmit buffer, a remote will attempt to transmit only every 2
N
hops.
Roughly speaking, this will proportionately reduce the average power consumption while
increasing average latency. When there are more than 16 remotes being operated, duty
cycling must be enabled since a maximum of 16 time slots is available per hop.
When a remote radio is powered up but is out of range of a base station, it will
continuous scan the frequency bands for the presence of a base radio. During this
scanning the radio can consume up to 70 mA of current at 3.3-volts. The WIT910
employs a switching regulator so the current consumption will be less at higher voltages.
2.3.4. RF Flow Control Mode
Because of slight differences in baud rates between transmitting and receiving hosts,
when sending large amounts of data (100’s of KB) in one direction in a point-to-point
application, it is possible to overrun the receive buffer of the receiving radio. For example
a nominal 57.6Kbaud at the transmitting radio’s host might really be 57,601 and at the
receiving radio’s host it might be 56,599. This is similar to a situation where the
transmitting radio is sent data at a higher baud rate than the baud rate at which data is
received by the receiving host. To compensate for the variations in nominal baud rates,
the WIT910 supports an RF flow control mode for point-to-point operation. In this mode,
when the receive buffer of the receiving WIT910 is close to full, the receiving WIT910
stops acknowledging transmissions. The transmitting radio is set to infinite retries which
invokes the RF flow control mode (See Set Packet Attempts Limit in Section 5.3). The
receiving radio will not begin acknowledging transmissions from the transmitting radio
until more room in the receive buffer has become available. This will cause data in the
transmit buffer of the transmitting radio to back up. If it backs up to the point where the
transmit buffer fills up, the transmitting radio will deassert CTS stopping data from the
transmitting radio’s host device. Once room is available in the receiving radio’s buffer,
the receiving radio will begin acknowledging transmissions from the transmitting radio
allowing the transmitting radio’s buffer to begin to empty which will cause the
transmitting radio to reassert CTS. Either one or both of the radios in a point-to-point
installation can be configured for the RF flow control. If this mode is invoked in a point-
to-multipoint installation, communications with all radios will be stopped when any one
radio’s receive buffer becomes full.
increasing average latency. When there are more than 16 remotes being operated, duty
cycling must be enabled since a maximum of 16 time slots is available per hop.
When a remote radio is powered up but is out of range of a base station, it will
continuous scan the frequency bands for the presence of a base radio. During this
scanning the radio can consume up to 70 mA of current at 3.3-volts. The WIT910
employs a switching regulator so the current consumption will be less at higher voltages.
2.3.4. RF Flow Control Mode
Because of slight differences in baud rates between transmitting and receiving hosts,
when sending large amounts of data (100’s of KB) in one direction in a point-to-point
application, it is possible to overrun the receive buffer of the receiving radio. For example
a nominal 57.6Kbaud at the transmitting radio’s host might really be 57,601 and at the
receiving radio’s host it might be 56,599. This is similar to a situation where the
transmitting radio is sent data at a higher baud rate than the baud rate at which data is
received by the receiving host. To compensate for the variations in nominal baud rates,
the WIT910 supports an RF flow control mode for point-to-point operation. In this mode,
when the receive buffer of the receiving WIT910 is close to full, the receiving WIT910
stops acknowledging transmissions. The transmitting radio is set to infinite retries which
invokes the RF flow control mode (See Set Packet Attempts Limit in Section 5.3). The
receiving radio will not begin acknowledging transmissions from the transmitting radio
until more room in the receive buffer has become available. This will cause data in the
transmit buffer of the transmitting radio to back up. If it backs up to the point where the
transmit buffer fills up, the transmitting radio will deassert CTS stopping data from the
transmitting radio’s host device. Once room is available in the receiving radio’s buffer,
the receiving radio will begin acknowledging transmissions from the transmitting radio
allowing the transmitting radio’s buffer to begin to empty which will cause the
transmitting radio to reassert CTS. Either one or both of the radios in a point-to-point
installation can be configured for the RF flow control. If this mode is invoked in a point-
to-multipoint installation, communications with all radios will be stopped when any one
radio’s receive buffer becomes full.
© 2000- 2004 Cirronet™ Inc
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