DSP56F826 datasheet(32/60 Pages) FREESCALE

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56F827 Technical Data, Rev. 12

Freescale Semiconductor

3.6.3

External Clock Source

The recommended method of connecting an external clock is given in Figure 3-11. The external clock

source is connected to XTAL and the EXTAL pin is held VDDA/2.

Figure 3-11 Connecting an External Clock Signal

Figure 3-12 External Clock Timing

Table 3-8 External Clock Operation Timing Requirements

Operating Conditions: VSSIO=VSS = VSSA = 0V, VDDA =VDDIO=3.0–3.6V, VDD = 2.25–2.75V, TA = –40° to +85°C, CL ≤ 50pF, fop = 80MHz

Characteristic

Symbol

Min

Typ

Max

Unit

Frequency of operation (external clock driver)1

1. See Figure 3-11 for details on using the recommended connection of an external clock driver.

fosc

802

2. When using Time-of-Day (TOD), maximum external frequency is 6MHz.

MHz

Clock Pulse Width3, 4

3. The high or low pulse width must be no smaller than 6.25ns or the chip will not function.

4. Parameters listed are guaranteed by design.

tPW

6.25

—

56F827

XTAL

EXTAL

External

VDDA/2

Clock

External

Clock

VIH

VIL

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

90%

50%

10%

90%

50%

10%

tPW

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