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2.3.3 Clock Doubler
The clock doubler allows a lower frequency crystal to be used for the main oscillator and
to provide an added range over which the clock frequency can be adjusted. The clock dou-
bler is controlled via the Global Clock Double Register (GCDR).
The clock doubler uses an on-chip delay circuit that must be programmed by the user at
startup if there is a need to double the clock. Table 2-3 lists the recommended delays for
the GCDR for various oscillator frequencies.
Table 2-3. Recommended Delays Set In GCDR for Clock Doubler
Recommended GCDR Value
Frequency Range
0x0F
≤
7.3728 MHz
0x0B
7.3728–11.0592 MHz
0x09
11.0592–16.5888 MHz
0x06
16.5888–20.2752 MHz
0x03
20.2752–52.8384 MHz
0x01
52.8384–70.0416 MHz
0x00
>70.0416 MHz
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