Murata Electronics North America DNT900 Manual Do Utilizador
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©2008 by RF Monolithics, Inc.
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DNT900 - 11/05/08
Setting the hop duration to 7.55 ms, the average full-duplex serial port byte rate that can be supported
under error free conditions is:
under error free conditions is:
128 Bytes /7.55 ms = 16.942 kB/s, or 169.42 kb/s for 8N1
Continuous full-duplex serial port data streams at a baud rate of 115.2 k/bs can be supported by this
configuration, provided only occasional RF transmission errors occur. Plan on an average serial port data
flow of 75% of the calculated error-free capacity for general-purpose applications, and 50% of the calcu-
lated error-free capacity for RF challenging applications such as vehicle telemetry and heavy industrial
process environments.
configuration, provided only occasional RF transmission errors occur. Plan on an average serial port data
flow of 75% of the calculated error-free capacity for general-purpose applications, and 50% of the calcu-
lated error-free capacity for RF challenging applications such as vehicle telemetry and heavy industrial
process environments.
Most applications do not require continuous serial port data flow. The DNT900 transmit and receive
buffers hold at least 1024 bytes and will accept brief bursts of data at high baud rates, provided the aver-
age serial port data flow such as shown in the example above is not exceeded. It is strongly recom-
mended that the DNT900 host use hardware flow control. The host must send no more than 32 bytes
additional bytes to the DNT900 when the DNT900 de-asserts the host’s CTS line. In turn, the DNT900 will
send no more than one byte following the host de-asserting its RTS line. Three-wire serial port operation
is allowed by connecting the DNT900 CTS output to its RTS input. However, three-wire operation should
be limited to applications that send small bursts of data occasionally at an average serial port data flow
less than 50% of the calculated error-free capacity. Data loss is possible under adverse RF channel
conditions when using three-wire serial operation.
buffers hold at least 1024 bytes and will accept brief bursts of data at high baud rates, provided the aver-
age serial port data flow such as shown in the example above is not exceeded. It is strongly recom-
mended that the DNT900 host use hardware flow control. The host must send no more than 32 bytes
additional bytes to the DNT900 when the DNT900 de-asserts the host’s CTS line. In turn, the DNT900 will
send no more than one byte following the host de-asserting its RTS line. Three-wire serial port operation
is allowed by connecting the DNT900 CTS output to its RTS input. However, three-wire operation should
be limited to applications that send small bursts of data occasionally at an average serial port data flow
less than 50% of the calculated error-free capacity. Data loss is possible under adverse RF channel
conditions when using three-wire serial operation.
2.10 Sleep Modes
To save power in applications where a remote transmits infrequently, the DNT900 supports a hardware
sleep mode. Hardware sleep mode is entered by switching DTR Pin 11 on the DNT900 from logic low to
high. While in hardware sleep mode, the DNT900 consumes less than 0.5 mA. This mode allows a
DNT900 to be powered off while its host device remains powered. After leaving hardware sleep mode
(Pin 11 low to high), the radio must re-synchronize with the base station and re-register.
sleep mode. Hardware sleep mode is entered by switching DTR Pin 11 on the DNT900 from logic low to
high. While in hardware sleep mode, the DNT900 consumes less than 0.5 mA. This mode allows a
DNT900 to be powered off while its host device remains powered. After leaving hardware sleep mode
(Pin 11 low to high), the radio must re-synchronize with the base station and re-register.
In addition to the sleep mode controlled by the DTR pin, in CSMA mode the DNT900 remotes support an
additional sleep mode to support battery-powered applications. When this mode is enabled, the DNT900
is in a low-power state and only wakes up in response to the I/O report triggers. The following list explains
the rules that sleeping remotes follow:
additional sleep mode to support battery-powered applications. When this mode is enabled, the DNT900
is in a low-power state and only wakes up in response to the I/O report triggers. The following list explains
the rules that sleeping remotes follow:
The DNT900 will wake up when any of the enabled I/O report trigger conditions fire. When any of
the ADC triggers are enabled, the radio will also wake up every ADC_SampleIntvl long enough to
sample the ADCs, and then go back to sleep.
sample the ADCs, and then go back to sleep.
When a sleeping radio wakes up, it must acquire and synchronize to its base before it can send
or receive any data. To prevent excessive battery use, if the remote is unable to acquire before
the WakeLinkTimeout elapses, it will cancel any pending event trigger(s) and go back to sleep.
the WakeLinkTimeout elapses, it will cancel any pending event trigger(s) and go back to sleep.
If a remote is linking for the first time or if its last attempt to acquire and synchronize was unsuc-
cessful, it will scan and record the entire broadcast system parameter list before it goes back to
sleep. Otherwise, in order to conserve battery life, a sleeping remote will update any values that it
may hear while it is awake, but is not required to listen to the entire list.
cessful, it will scan and record the entire broadcast system parameter list before it goes back to
sleep. Otherwise, in order to conserve battery life, a sleeping remote will update any values that it
may hear while it is awake, but is not required to listen to the entire list.