ade7566 Analog Devices, Inc., ade7566 Datasheet - Page 107

• Manufacturer Part Number: ade7566
• Description: Single-phase Energy Measurement Ic With 8052 Mcu, Rtc, And Lcd Driver
• Manufacturer: Analog Devices, Inc.

REAL TIME CLOCK
The ADE7566/ADE7569 have an embedded real time clock
(RTC) as shown in Figure 96. 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.
CALIBRATED
32.768kHz
HUNDREDTHS COUNTER
INTERVAL COUNTER
SECOND COUNTER
MINUTE COUNTER
HOUR COUNTER
PRESCALER
INTVAL SFR
32.768kHz
CRYSTAL
HTHSEC
HOUR
8-BIT
8-BIT
SEC
MIN
RTCEN
Figure 96. RTC Implementation
RTCCOMP
CALIBRATION
EQUAL?
TEMPCAL
MIDNIGHT EVENT
SELECTION
ITS1
TIMEBASE
INTERVAL
MUX
ITS0
ALARM
EVENT
ITEN
Rev. 0 | Page 107 of 136
RTC REGISTERS
Note that all the real time clock SFRs are not bit addressable.
Table 117. Real Time Clock SFR
SFR
TIMECON
HTHSEC
SEC
MIN
HOUR
INTVAL
RTCCOMP
TEMPCAL
Protecting the RTC from Runaway Code
To protect the RTC from runaway code, a key must be written
to the KYREG register to obtain write access to the Interrupt
Pins Configuration SFR (INTPR, 0xFF), Hundredths of a
Second Counter SFR (HTHSEC, 0xA2), Seconds Counter SFR
(SEC, 0xA3), Minutes Counter SFR (MIN, 0xA4), and Hours
Counter SFR (HOUR, 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
MOV
KYREG,#0EAh
INTPR,#080h
Address
0xA1
0xA2
0xA3
0xA4
0xA5
0xA6
0xF6
0xF7
Description
RTC Configuration (see Table 118).
Hundredths of a Second Counter
(see Table 119).
Seconds Counter (see Table 120).
Minutes Counter (see Table 121).
Hours Counter (see Table 122).
Alarm Interval (see Table 123).
RTC Nominal Compensation
(see Table 124).
RTC Temperature Compensation
(see Table 125).
ADE7566/ADE7569