EZ80F91MCU Datasheet, PDF (185/396 Pages) Zilog, Inc. – eZ80Acclaim-TM Flash Microcontrollers

eZ80F91 MCU
Product Specification
166
Real-Time Clock
Real-Time Clock Overview
The Real-Time Clock (RTC) keeps time by maintaining a count of seconds, min-
utes, hours, day-of-the-week, day-of-the-month, year, and century. The current
time is kept in 24-hour format. The format for all count and alarm registers is
selectable between binary and binary-coded-decimal (BCD) operations. The cal-
endar operation maintains the correct day of the month and automatically com-
pensates for leap year. A simplified block diagram of the RTC and the associated
on-chip, low-power, 32 KHz oscillator is illustrated in Figure 34. Connections to an
external battery supply and 32 KHz crystal network are also demonstrated in
Figure 34.
V_DD
IRQ
Real-Time Clock
ADDR[15:0]
RTC_V_DD
Battery
DATA[7:0]
RTC Clock
R1
RTC_X_OUT
System Clock
C
Low-Power
32 KHz Oscillator
V_DD
32 KHz
Crystal
Enable
CLK_SEL
(RTC_CTRL[4])
RTC_X_IN
C
Figure 34. Real-Time Clock and 32KHz Oscillator Block Diagram
PS019209-0504
PRELIMINARY
Real-Time Clock