191
CHAPTER 13 PLL FREQUENCY SYNTHESIZER
User’s Manual U15104EJ2V0UD
Because the least significant bit of the division value N must be set to bit 7 (PLLSCN) of PLL data register
0 (PLLR0), data must be set by shifting the result of the above calculation 1 bit to the right.
Data is set to the PLL data registers (PLLR and PLLR0) as follows.
After setting the above PLL data registers (PLLR and PLLR0), data must be transferred to the
programmable counter and swallow counter by setting bit 0 (PLLNS0) of the PLL data transfer register
(PLLNS).
In this example, a value of half the N value is set to the high-order 16 bits of the PLL data register (PLLR)
by shifting the N value resulting from calculation 1 bit to the right.
If the N value is calculated as follows with the least significant bit of the N value in PLLSCN fixed to 0,
the result of the calculation (N
PLLR
) can be set to the PLL data register (PLLR) as is.
If the calculation result is set in this way, however, the input frequency (f
VCOL
) is 2
×
f
r
(reference frequency)
of the set value N
PLLR
.
N
PLLR
=
f
VCOL
2f
r
PLLR
Programmable counter value
Fixed to 0
PLLRL
PLLRH
b7
b16
b6
b15
b5
b14
b4
b13
b3
b12
b2
b11
b1
b10
b0
b9
b7
b8
b6
b7
b5
b6
b4
b5
0
0
0
0
5
1
1
0
0
5
1
1
H
0
0
1
0
1
0
0
0
1
0
0
0
0
1
b3
b4
b2
b3
b1
b2
b0
b1
b7
b0
b6 b5 b4 b3 b2 b1 b0
PLLR0
PLLSCN
Value shifted 1 bit to right
0
0
0
0
0
1
0
1
0
0
0
1
0
0
0
1
0
0
Shifted 1 bit to right
A
2
3
H
Result of calculation (N value)
0
0
0
0
1
0
1
0
0
0
1
0
0
0
1
1
Swallow counter value
Содержание mPD178053
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