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Distributor of Digi International: Excellent Integrated System Limited
Datasheet of 101-0533 - KIT DEV RABBIT3000/RCM3100
Contact us: sales@integrated-circuit.com Website: www.integrated-circuit.com
4.4 Other Hardware
4.4.1 Clock Doubler
The RCM3100 takes advantage of the Rabbit 3000 microprocessor's internal clock dou-
bler. A built-in clock doubler allows half-frequency crystals to be used to reduce radiated
emissions. The 29.4 MHz frequency specified for the RCM3100 is generated using a
14.7456 MHz crystal. The clock doubler will not work for crystals with a frequency
above 26.7264 MHz.
The clock doubler may be disabled if 29.4 MHz clock speeds are not required. Disabling
the Rabbit 3000 microprocessor's internal clock doubler will reduce power consumption
and further reduce radiated emissions. The clock doubler is disabled with a simple config-
uration macro as shown below.
1. Select the "Defines" tab from the Dynamic C
2. Add the line
CLOCK_DOUBLED=0
The clock doubler is enabled by default, and usually no entry is needed. If you need to
specify that the clock doubler is always enabled, add the line
always enable the clock doubler.
3. Click
to save the macro. The clock doubler will now remain off whenever you are
OK
in the project file where you defined the macro.
4.4.2 Spectrum Spreader
The Rabbit 3000 features a spectrum spreader, which helps to mitigate EMI problems. By
default, the spectrum spreader is on automatically, but it may also be turned off or set to a
stronger setting. The means for doing so is through a simple configuration macro as shown
below.
1. Select the "Defines" tab from the Dynamic C
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 unnecessary for the BL2000.
3. Click
to save the macro. The spectrum spreader will now remain off whenever you
OK
are in the project file where you defined the macro.
NOTE: Refer to the Rabbit 3000 Microprocessor User's Manual for more information
on the spectrum-spreading setting and the maximum clock speed.
User's Manual
Options > Project Options
to always disable the clock doubler.
Options > Project Options
menu.
to
CLOCK_DOUBLED=1
menu.
27
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