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CHAPTER 13 PLL FREQUENCY SYNTHESIZER
User’s Manual U15104EJ2V0UD
(3) Pulse swallow mode (VHF)
(a) Calculating division value N (value set to PLL data register)
N =
f
VCOH
f
r
where,
f
VCOH
: Input frequency of VCOH pin
f
r
:
Reference frequency
(b) Example of setting PLL data register
An example of setting the PLL data register to receive broadcasting stations in the following FM band
is shown below.
Receive frequency:
100.0 MHz (FM band)
Reference frequency:
50 kHz
Intermediate frequency: +10.7 MHz
Division value N is calculated as follows:
N =
f
VCOH
=
100.0 + 10.7
= 2214 (decimal)
f
r
0.05
= 08A6H (hexadecimal)
Because the least significant bit of the division value N must be set to the PLL data register 0 (PLLR0),
data must be set by shifting the value calculated by the above expression 1 bit to the right.
Data is set to the PLL data registers (PLLR and PLLR0) as follows.
PLLR
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
4
5
3
0
0
4
5
3
H
0
0
1
0
0
0
0
1
1
0
0
1
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
0
0
1
0
1
0
0
1
1
0
0
Shifted 1 bit to right
8
A
6
H
Result of calculation (N value)
0
0
0
0
1
0
0
0
1
0
1
0
0
1
1
0
Programmable counter value
Fixed to 0
Swallow counter value