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CHAPTER 13 PLL FREQUENCY SYNTHESIZER
User’s Manual U15104EJ2V0UD
(5) Operation of unlock F/F
The unlock F/F detects the unlock status of the PLL frequency synthesizer.
The unlock status of the PLL frequency synthesizer is detected from the up request signal UP and down request
signal DW of the phase comparator (
φ
-DET).
Because either of the up request or down request signal outputs a low level in the unlock status, the unlock
status can be detected by using this low-level signal.
The status of the unlock F/F is detected by bit 0 (PLLUL0) of the PLL unlock F/F judge register (PLLUL).
The unlock F/F is set at the cycle of reference frequency f
r
selected at that time.
The PLL unlock F/F judge register is reset when its contents have been read.
To read the PLLUL, therefore, it must be read at a cycle longer than the cycle (1/f
r
) of the reference frequency.
13.4.2 Operation to set N value of PLL frequency synthesizer
The division value (N value) is set to the programmable counter (12 bits) and swallow counter (5 bits) by the PLL
data registers (PLLRL, PLLRH, and PLLR0).
When the N value has been transferred to the programmable counter and swallow counter by bit 0 (PLLNS0) of
the PLL data transfer register (PLLNS), frequency division is carried out in the selected division mode.
Examples of setting the N value in the respective division modes (MF, HF, and VHF) are shown below.
(1) Direct division mode (MF)
(a) Calculating division value N (value set to PLL data register)
N =
f
VCOL
f
r
where,
f
VCOL
:
Input frequency of V
COL
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 MW band
is shown below.
Receive frequency:
1422 kHz (MW band)
Reference frequency:
9 kHz
Intermediate frequency: 450 kHz
Division value N is calculated as follows:
N =
f
VCOL
=
1422 + 450
= 208 (decimal)
f
r
9
= 0D0H (hexadecimal)
Содержание mPD178053
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