NEC PD17062 - Manual (Page 222)

222
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PD17062
18.3.2 Programmable Divider (PD) and Data Buffer (DBF)
The programmable divider divides the frequency of an input signal at the VCO pin by the values specified
in the swallow counter and programmable counter.
The swallow and programmable counters consist of a 4- and 12-bit binary downcounter, respectively.
The swallow and programmable counters are loaded with a division value by setting it in the PLL data
register (PLLR, at address 41H) through the data buffer (DBF).
Writing to and reading from the PLL data register are performed with the “PUT PLLR,DBF” and “GET
DBF,PLLR” instructions respectively.
A division value is called an N-value.
The following expression represents the frequency “f
N
” of a signal generated in the programmable divider
using the value N in the PLL data register (PLLR).
Pulse swallow method
f N =
f
in
(where N is 16 bits)
N
See Section 18.7 for how to set the division value (N-value) for each frequency division method.