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3.7
EXTERNAL CLOCK OPERATION
The DSP56367 system clock is an externally supplied square wave voltage source connected
to EXTAL(Figure 3-1).
EXTAL
V
ILC
Note:
The midpoint is 0.5 (V
No.
1
Frequency of EXTAL (EXTAL Pin Frequency)
The rise and fall time of this external clock should be 3 ns
maximum.
2
EXTAL input high
•
With PLL disabled (46.7%–53.3% duty
cycle
•
With PLL enabled (42.5%–57.5% duty
cycle
3
EXTAL input low
•
With PLL disabled (46.7%–53.3% duty
cycle
•
With PLL enabled (42.5%–57.5% duty
cycle
4
EXTAL cycle time
•
With PLL disabled
•
With PLL enabled
7
Instruction cycle time = I
•
With PLL disabled
•
With PLL enabled
MOTOROLA
ET
ET
H
L
2
3
4
ET
C
+ V
).
IHC
ILC
Figure 3-1 E
Table 3-5 Clock Operation
Characteristics
1, 2
6
)
6
)
1, 2
6
)
6
)
2
4
= T
CYC
C
DSP56367
Midpoint
xternal Clock Timing
Symbol
Ef
ET
H
ET
L
ET
C
I
CYC
Specifications
External Clock Operation
V
IHC
Min
Max
0
120.0
∞
3.89 ns
157.0 µs
3.54 ns
∞
3.89 ns
157.0 µs
3.54 ns
∞
8.33 ns
273.1 µs
8.33 ns
∞
16.66 ns
8.53 µs
8.33 ns
3-7
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