Rabbit Coyote BL2500, Руководство пользователя

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34 Coyote (BL2500)
3.7 Other Hardware
3.7.1 Clock Doubler
The Coyote takes advantage of the Rabbit 3000 microprocessor’s internal clock doubler.
A built-in clock doubler allows half-frequency crystals to be used to reduce radiated
emissions. The 29.4 MHz frequency specified for the Coyote 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.
NOTE: Disabling the clock doubler will degrade the A/D and D/A conversion.
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.
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.