PCF5271CVM100 datasheet(20/56 Pages) FREESCALE

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MCF5271 Integrated Microprocessor Hardware Specification, Rev. 1.2

Design Recommendations

Freescale Semiconductor

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.

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