DSP56852PB View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

Manufacturer

DSP56852PB

16-bit Digital Signal Processor

Motorola => Freescale 

Freescale Semiconductor, Inc.

4.4 AC Electrical Characteristics

Timing waveforms in Section 4.2 are tested with a VIL maximum of 0.8V and a VIH minimum of 2.0V for

all pins except XTAL, which is tested using the input levels in Section 4.2. In Figure 6 the levels of VIH

and VIL for an input signal are shown.

VIH

Low

Input Signal

Midpoint1

Fall Time

VIL

High

Rise Time

90%

50%

10%

Note: The midpoint is VIL + (VIH – VIL)/2.

Figure 6. Input Signal Measurement References

Figure 7 shows the definitions of the following signal states:

• Active state, when a bus or signal is driven, and enters a low impedance state

• Tri-stated, when a bus or signal is placed in a high impedance state

• Data Valid state, when a signal level has reached VOL or VOH

• Data Invalid state, when a signal level is in transition between VOL and VOH

Data1 Valid

Data1

Data2 Valid

Data2

Data Invalid State

Data Active

Data

Tri-stated

Data3 Valid

Data3

Data Active

Figure 7. Signal States

4.5 External Clock Operation

The DSP56852 system clock can be derived from a crystal or an external system clock signal. To generate

a reference frequency using the internal oscillator, a reference crystal must be connected between the

EXTAL and XTAL pins.

4.5.1 Crystal Oscillator for use with PLL

The internal oscillator is designed to interface with a parallel-resonant crystal resonator in the frequency

range specified for the external crystal in Table 9. In Figure 8 a typical crystal oscillator circuit is shown.

Follow the crystal supplier’s recommendations when selecting a crystal, because crystal parameters

determine the component values required to provide maximum stability and reliable start-up. The crystal

and associated components should be mounted as close as possible to the EXTAL and XTAL pins to

minimize output distortion and start-up stabilization time.

18

DSP56852 Technical Data

For More Information On This Product,

Preliminary

Go to: www.freescale.com

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