參數(shù)資料
型號: 20-101-1094
廠商: Rabbit Semiconductor
文件頁數(shù): 75/130頁
文件大?。?/td> 0K
描述: MCU RCM4000 RABBITCORE
標(biāo)準(zhǔn)包裝: 1
系列: RabbitCore®
模塊/板類型: MPU 核心模塊
適用于相關(guān)產(chǎn)品: RCM4000
產(chǎn)品目錄頁面: 619 (CN2011-ZH PDF)
其它名稱: 316-1139
User’s Manual
43
4.5 Other Hardware
4.5.1 Clock Doubler
The RCM4000 takes advantage of the Rabbit 4000 microprocessor’s internal clock doubler.
A built-in clock doubler allows half-frequency crystals to be used to reduce radiated
emissions. The 58.98 MHz frequency specified for the RCM4000 is generated using a
29.49 MHz crystal.
The clock doubler may be disabled if 58.98 MHz clock speeds are not required. Disabling
the Rabbit 4000 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.
4.5.2 Spectrum Spreader
The Rabbit 4000 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 means for doing so is through a simple configuration macro as shown below.
NOTE: Refer to the Rabbit 4000 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
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 set-
ting will be used in a real application.
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.
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