LC7219M View Datasheet(PDF) - SANYO -> Panasonic

Part Name

Description

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LC7219M

PLL Frequency Synthesizers

SANYO -> Panasonic 

LC7219, 7219M

General-purpose Counter

The 20-bit general-purpose counter is used for both frequency and period measurement as shown in figure 8. The

measurement mode is selected by bits SC and SF as shown in table 7. The counter value is output on DO with the msb

first.

Figure 8. General-purpose counter

Table 7. General-purpose counter mode selection

SC

SF

Input port

Parameter

1

×

0

1

0

0

HCTR

LCTR

LCTR

Frequency measurement (sine wave)

Frequency measurement (sine wave)

Period measurement (pulse wave)

Note

× = don’t care

In frequency measurement mode, the input cycles during a 30 or 60 ms interval are counted. Either LCTR or HCTR

can be selected as the counter input.

In period measurement mode, LCTR is the single input, and the 900kHz cycles in one or two periods of the LCTR

signal are counted.

The counter starts when the CTEN flag is set. The serial input data is latched in on the falling edge of CE. The input

data on HCTR or LCTR should be input within 10 ms of this transition.

The period or frequency measurement count should be read while CTEN is still set to 1, as the counter is reset by

setting CTEN to 0. CTEN should be set to 0 before each measurement.

The LCTR signal is passed directly to the counter input. The HCTR signal is passed through a divide-by-eight

prescaler. The actual HCTR frequency is, therefore, eight times the measured frequency.

When the universal counter is used as the IF counter, the state of the IF-IC SD (station detect) signal must be checked

by the microcontroller, and the IF counter buffer output turned on only after the SD signals are activated. Auto-search

techniques using only the IF counter are not advisable since it is possible that the search can stop incorrectly at a

location that does not have a station due to the IF counter buffer output leakage.

DO goes HIGH when the CTEN flag is set to 1, and LOW when frequency or period measurement is completed. DO

can be monitored to check for measurement completion. The timing for the general-purpose counter is shown in figure

9.

No.3661–8/12

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