WIT2450
©
2000- 2005 Cirronet
™
Inc
28
M-2450-0000 Rev B
base slot size allows the base to send 32 bytes of data per hop. The
90H
hop duration
provides a 10ms hop dwell time. These default settings provide a base throughput of
40kbps (Since the over the air transmission is synchronous, the 32kbps synchronous over
the air rate is equivalent to 40kbps asynchronous into the radio serial port). If the base
transmits continuously at a higher rate than this, unless the default settings are changed,
the transmit buffer will eventually overflow. To allow a higher base throughput, either
increase the base slot size or the hop duration or both. A similar analysis needs to be
performed for the remote radios. Refer to
Section 2.2.3 TDMA Mode
for the remote
throughput calculation.
4.4. Power-On Reset Requirements
The WIT2450 has an internal reset circuit that provides a reset signal to the
microprocessor if the supply voltage to the WIT2450 falls below 2.7-volts. Operation of
the microprocessor at voltages below this voltage is unspecified and can result in
corruption of the program memory. When the radio is first powered on, there is an inrush
current in excess of 250mA. The power supply in the host must be capable of sourcing
this current without the voltage falling below 2.7-volts at the radio. Failure of the power
supply to meet this requirement can result in “motorboating” of the radio where the
inrush current of the radio pulls the supply voltage below 2.7-volts causing the reset
circuit to fire which resets the radio removing the current requirement. Once the voltage
recovers to a level above 2.7-volts, the reset signal is removed from the radio which
causes the inrush current which causes the voltage to drop causing the reset circuit to fire
and so on.
