DSP56F826PB 查看數據表（PDF） - Freescale Semiconductor

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DSP56F826PB

16-bit Digital Signal Controllers

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.

56F826

XTAL EXTAL

External VDDA/2

Clock

Figure 3-11 Connecting an External Clock Signal

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 fosc

0

4

802

Clock Pulse Width3, 4

tPW

6.25

—

—

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

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

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.

MHz

ns

External

Clock

90%

50%

10%

tPW

tPW

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

Figure 3-12 External Clock Timing

VIH

90%

50%

10%

VIL

56F826 Technical Data, Rev. 14

30

Freescale Semiconductor

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