26
RabbitCore RCM3000
4.4 Other Hardware
4.4.1 Clock Doubler
The RCM3000 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 RCM3000 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.
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.
NOTE:
Refer to the
Rabbit 3000 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. 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.
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 nor-
mal 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 set-
ting will be used 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.
Downloaded from
Elcodis.com
electronic components distributor
Summary of Contents for RabbitCore RCM3000
Page 8: ...RabbitCore RCM3000 Downloaded from Elcodis com electronic components distributor...
Page 36: ...28 RabbitCore RCM3000 Downloaded from Elcodis com electronic components distributor...
Page 42: ...34 RabbitCore RCM3000 Downloaded from Elcodis com electronic components distributor...
Page 56: ...48 RabbitCore RCM3000 Downloaded from Elcodis com electronic components distributor...
Page 80: ...72 RabbitCore RCM3000 Downloaded from Elcodis com electronic components distributor...
Page 110: ...102 RabbitCore RCM3000 Downloaded from Elcodis com electronic components distributor...
Page 126: ...118 RabbitCore RCM3000 Downloaded from Elcodis com electronic components distributor...
Page 128: ...Downloaded from Elcodis com electronic components distributor...
