Rabbit Smartcat, User Manual

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34 Smartcat (BL2100)
3.9.2 Clock Doubler
The BL2100 takes advantage of the Rabbit 2000 microprocessor’s internal clock doubler.
A built-in clock doubler allows half-frequency crystals to be used to reduce radiated emis-
sions. The 22.1 MHz frequency is generated using an 11.0592 MHz crystal. The clock
doubler is disabled automatically in the BIOS for crystals with a frequency above
12.9 MHz.
The clock doubler may be disabled if 22.1 MHz clock speeds are not required. Disabling
the Rabbit 2000 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.
3.9.3 Spectrum Spreader
BL2100 boards that carry the CE mark on their RabbitCore module have a Rabbit 2000
microprocessor that features a spectrum spreader, which helps to mitigate EMI problems.
By default, the spectrum spreader is on automatically for BL2100 boards that carry the CE
mark when used with Dynamic C 7.30 or later versions, but the spectrum spreader 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.
.
There is no spectrum spreader functionality for BL2100 boards that do not carry the CE
mark on their RabbitCore module or when using any BL2100 with a version of Dynamic C
prior to 7.30.
1.
Select the “Defines” tab from the Dynamic C
Options > Project Options menu.
2. Add the line
CLOCK_DOUBLED=0
to always disable the clock doubler.
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
CLOCK_DOUBLED=1
to always enable
the clock doubler. The clock speed will be doubled as long as the crystal frequency is
less than or equal to 26.7264 MHz.
3. Click OK
to save the macro. The clock doubler will now remain off whenever you are in the
project file where you defined the macro.
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 unnecessary for the BL2000.
3. Click
OK
to save the macro. The spectrum spreader will now be set to the state specified by
the macro value whenever you are in the project file where you defined the macro.