ADE7166_15 datasheet(121/152 Pages) AD

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ADE7116/ADE7156/ADE7166/ADE7169/ADE7566/ADE7569

Rev. B | Page 121 of 152

REAL-TIME CLOCK (RTC)

The ADE7116/ADE7156/ADE7166/ADE7169/ADE7566/

ADE7569 have an embedded real-time clock (RTC) as shown in

Figure 103. The external 32.768 kHz crystal is used as the clock

source for the RTC. Calibration is provided to compensate the

nominal crystal frequency and for variations in the external

crystal frequency over temperature. By default, the RTC is

maintained active in all power saving modes. The RTC counters

retain their values through watchdog resets and external resets.

They are only reset during a power-on reset.

8-BIT

PRESCALER

SECOND COUNTER

SEC

MINUTE COUNTER

MIN

HOUR COUNTER

HOUR

ITEN

ALARM

EVENT

8-BIT

INTERVAL COUNTER

INTVAL SFR

INTERVAL

TIMEBASE

SELECTION

MUX

RTCEN

32.768kHz

CRYSTAL

ITS1

ITS0

EQUAL?

CALIBRATION

RTCCOMP

TEMPCAL

MIDNIGHT EVENT

CALIBRATED

32.768kHz

HUNDREDTHS COUNTER

HTHSEC

Figure 103. RTC Implementation

RTC SFRS

Note that none of the real-time clock SFRs are bit addressable.

Table 127. Real-Time Clock SFR

SFR

Address

Description

TIMECON

0xA1

RTC Configuration (see Table 128).

HTHSEC

0xA2

Hundredths of a Second Counter

(see Table 129).

SEC

0xA3

Seconds Counter (see Table 130).

MIN

0xA4

Minutes Counter (see Table 131).

HOUR

0xA5

Hours Counter (see Table 132).

INTVAL

0xA6

Alarm Interval (see Table 133).

RTCCOMP

0xF6

RTC Nominal Compensation (see

Table 134).

TEMPCAL

0xF7

RTC Temperature Compensation (see

Table 135).

Protecting the RTC from Runaway Code

To protect the RTC from runaway code, a key must be written

to the KYREG SFR (Address, 0xC1) to obtain write access to the

interrupt pins configuration SFR (INTPR, Address 0xFF),

hundredths of a second counter SFR (HTHSEC, Address 0xA2),

seconds counter SFR (SEC, 0xA3), minutes counter SFR (MIN,

Address 0xA4), and hours counter SFR (HOUR, Address 0xA5).

KYREG should be set to 0xEA to unlock it and reset it to zero

after a timekeeping register is written to. The RTC registers can

be written using the following 8052 assembly code:

MOV

KYREG,#0EAh

MOV

INTPR,#080h

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