UPD17062 datasheet(230/298 Pages) RENESAS

230 / 298 page

228

µPD17062

18.5.3

Charge Pump

As shown in Fig. 18-5, the charge pump directs the up request signal (UP) or down request signal (DW)

from the phase comparator (

φ-DET) to the error output pin (EO) pin.

The relationships among the output at the error output pin, divider output frequency fN, and reference

frequency fr are as follows:

Reference frequency fr > divider output frequency fN: Low level output

Reference frequency fr < divider output frequency fN: High level output

Reference frequency fr = divider output frequency fN: Floating

18.5.4

Unlock Detection Block

As shown in Fig. 18-5, the unlock detection block detects the unlock state of the PLL frequency synthesizer

according to the up request signal (UP) or down request signal (DW) from the phase comparator (

φ-DET).

Either the up or down request signal is low in the unlock state. So the unlock detection block detects this

low signal as unlock state. When the unlock state is detected, the unlock flip-flop (FF) is set (1).

The state of the unlock FF is detected using the PLL unlock FF judge register (at address 22H).

The unlock FF is set at intervals of the then selected reference frequency fr.

The unlock FF is reset when the PLL unlock FF judge register is read-accessed with a PEEK instruction.

The unlock FF must be checked at intervals greater than the period (1/fr) of the reference frequency fr.

The unlock delay control circuit controls whether to set the unlock FF, by delaying the up and down request

signals output from the phase comparator.

If the delay becomes large, the unlock FF will not be set even if the phase difference between the divider

output frequency fN and reference frequency fr is large.

The delay is specified in the unlock delay control circuit using the PLL unlock FF delay control register (at

address 32H).

The following paragraphs describe the configuration and functions of the PLL unlock FF judge register and

PLL unlock FF delay control register.

UPD17062 Datasheet(PDF) 230 Page - Renesas Technology Corp