Rabbit RabbitCore RCM5400W, Руководство пользователя

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44 RabbitCore RCM5400W
4.5 Other Hardware
4.5.1 Clock Doubler
The RCM5400W takes advantage of the Rabbit 5000 microprocessor’s internal clock
doubler. A built-in clock doubler allows half-frequency crystals to be used to reduce
radiated emissions. The 73.73 MHz frequency specified for the RCM5400W is generated
using a 36.864 MHz crystal.
The clock doubler should not be disabled since Wi-Fi operations depend highly on CPU
resources.
4.5.2 Spectrum Spreader
The Rabbit 5000 features a spectrum spreader, which helps to mitigate EMI problems. The
spectrum spreader is on by default, but it may also be turned off or set to a stronger setting.
The spectrum spreader settings may be changed through a simple configuration macro as
shown below.
NOTE: Refer to the Rabbit 5000 Microprocessor User’s Manual for more information
on the spectrum-spreading setting and the maximum clock speed.
1. Select the “Defines” tab from the Dynamic C Options > Project Options menu.
2. Normal spreading is the default, and usually no entry is needed. If you need to specify
normal spreading, add the line
ENABLE_SPREADER=1
For strong spreading, add the line
ENABLE_SPREADER=2
To disable the spectrum spreader, add the line
ENABLE_SPREADER=0
NOTE: The strong spectrum-spreading setting is not recommended since it may limit
the maximum clock speed or the maximum baud rate. It is unlikely that the strong
setting will be needed in a real application.
3. Click OK to save the macro. The spectrum spreader will now remain off whenever you
are in the project file where you defined the macro.