參數(shù)資料
型號(hào): IBM25PPC405GP-3DD200C
元件分類(lèi): 微控制器/微處理器
英文描述: RISC PROCESSOR, PBGA456
封裝: 27 MM, PLASTIC, BGA-456
文件頁(yè)數(shù): 44/58頁(yè)
文件大小: 878K
代理商: IBM25PPC405GP-3DD200C
PowerPC 405GP Embedded Processor Data Sheet
49
Spread Spectrum Clocking
Care must be taken when using a spread spectrum clock generator (SSCG) with the PPC405GP. This
controller uses a PLL for clock generation inside the chip. The accuracy with which the PLL follows the SSCG
is referred to as tracking skew. The PLL bandwidth and phase angle determine how much tracking skew
there is between the SSCG and the PLL for a given frequency deviation and modulation frequency. When
using an SSCG with the PPC405GP the following conditions must be met:
The frequency deviation must not violate the minimum clock cycle time. Therefore, when operating the
PPC405GP with one or more internal clocks at their maximum supported frequency, the SSCG can only
lower the frequency.
The maximum frequency deviation cannot exceed
3%, and the modulation frequency cannot exceed
40kHz. In some cases, on-board PPC405GP peripherals impose more stringent requirements (see
Note 1).
Use the Peripheral Bus Clock for logic that is synchronous to the peripheral bus since this clock tracks the
modulation.
Use the SDRAM MemClk since it also tracks the modulation.
Notes:
1. The PCI clock specification for 66MHz allows a maximum frequency deviation of
1% at a modulation
between 30kHz and 33kHz. PCI asynchronous mode is unaffected.
2. The serial port baud rates are synchronous to the modulated clock. The serial port has a tolerance of
approximately 1.5% on baud rate before framing errors begin to occur. The 1.5% tolerance assumes that
the connected device is running at precise baud rates. If an external serial clock is used the baud rate is
unaffected by the modulation
3. Ethernet operation is unaffected.
4. IIC operation is unaffected.
Caution: It is up to the system designer to ensure that any SSCG used with the PPC405GP meets the
above requirements and does not adversely affect other aspects of the system.
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IBM25PPC405GP-3DE200C 制造商:IBM 功能描述:Microprocessor, 32 Bit, 456 Pin, Plastic, BGA
IBM25PPC405GP3DE200CZ 制造商:未知廠(chǎng)家 制造商全稱(chēng):未知廠(chǎng)家 功能描述:MICROPROCESSOR|32-BIT|CMOS|BGA|456PIN|PLASTIC
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IBM25PPC405GP3DE266CZ 制造商:未知廠(chǎng)家 制造商全稱(chēng):未知廠(chǎng)家 功能描述:MICROPROCESSOR|32-BIT|CMOS|BGA|456PIN|PLASTIC
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