MCF5271 查看數據表（PDF） - Freescale Semiconductor

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MCF5271

MCF5271 Integrated Microprocessor Hardware Specification

Freescale Semiconductor 

Design Recommendations

6.2 Power Supply

• 33 µF, .1 µF and .01 µF across each power supply

6.3 Decoupling

• Place the decoupling caps as close to the pins as possible, but they can be outside the footprint of

the package.

• .1 µF and .01 µF at each supply input

6.4 Buffering

• Use bus buffers on all data/address lines for all off-board accesses and for all on-board accesses

when excessive loading is expected. See Section 8, “Preliminary Electrical Characteristics.”

6.5 Pull-up Recommendations

• Use external pull-up resistors on unused inputs. See pin table.

6.6 Clocking Recommendations

• Use a multi-layer board with a separate ground plane.

• Place the crystal and all other associated components as close to the EXTAL and XTAL

(oscillator pins) as possible.

• Do not run a high frequency trace around crystal circuit.

• Ensure that the ground for the bypass capacitors is connected to a solid ground trace.

• Tie the ground trace to the ground pin nearest EXTAL and XTAL. This prevents large loop

currents in the vicinity of the crystal.

• Tie the ground pin to the most solid ground in the system.

• Do not connect the trace that connects the oscillator and the ground plane to any other circuit

element. This tends to make the oscillator unstable.

• Tie XTAL to ground when an external oscillator is clocking the device.

6.7 Interface Recommendations

6.7.1 SDRAM Controller

6.7.1.1 SDRAM Controller Signals in Synchronous Mode

Table 4 shows the behavior of SDRAM signals in synchronous mode.

MCF5271 Integrated Microprocessor Hardware Specification, Rev. 1.2

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Freescale Semiconductor

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