Altera Stratix II GX EP2SGX90 Transceiver Signal Integrit Manual de usuario descargar pdf (Pagina 20)

2–10 Reference Manual Altera Corporation

Stratix II GX EP2SGX90 Transceiver Signal Integrity Development Board May 2006

Clocking Circuitry

ICS557-03 (U5): Spread Spectrum Clock Generator for PCI-Express

The ICS557-03 is a spread spectrum clock generator supporting PCIe and

Ethernet protocol requirements. The device is used to substantially

reduce electromagnetic interference (EMI) in PC or embedded systems.

The device provides two differential spread spectrum outputs, and is pin-

configured for clock and spread selection. Using phase-locked loop (PLL)

techniques, the device takes a 25 MHz crystal input and produces two

pairs of differential outputs (HCSL) at 25 MHz, 100 MHz, 125 MHz and

200 MHz clock frequencies. The device also provides spread selection of

±0.25%, -0.5%, -0.75%, and no spread.

Table 2–5 lists output clock DIP switch settings.

Table 2–6 lists spread spectrum output selection DIP switch settings.

Table 2–5. Output Clock Setting DIP Switch Pinout (S8)

Switch 25 MHz 100 MHz 125 MHz 200 MHz

SW1 Closed Open Closed Open

SW2 Closed Closed Open Open

Table 2–6. Spread Spectrum Output Selection Setting (S8)

Switch Center =/-0.25 Down -0.5 Down -0.75 No Spread

SW3 Closed Open Closed Open

SW4 Closed Closed Open Open

1 2 ... 15 16 17 18 19 20 21 22 23 24 25 ... 39 40

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Altera Stratix II GX EP2SGX90 Transceiver Signal Integrit Manual de usuario Pagina 20