Micro Crystal

Real Time Clock / Calendar Module

RV-8564

8/40

6. FUNCTIONAL DESCRIPTION

The RV-8564 RTC module combines a RTC IC with on chip oscillator together with a 32.768 kHz quartz crystal in a

miniature ceramic package.

The RV-8564 contains sixteen 8-bit registers with an auto-incrementing address register, a frequency divider which

provides the source clock for the Real Time Clock (RTC), a programmable clock output, a timer, a voltage low

detector and a 400 kHz I

All 16 registers are designed as addressable 8-bit parallel registers although not all bits are implemented. The first

two registers (memory address 00h and 01h) are used as control and/or status registers. The memory addresses

02h through 08h are used as counters for the clock function (seconds up to year counters). Address locations 09h

through 0Ch contain alarm registers which define the conditions for an alarm. Address 0Dh controls the CLKOUT

output frequency. 0Eh and 0Fh are the timer control and timer registers, respectively.

The seconds, minutes, hours, days, weekdays, months, years as well as the minute alarm, hour alarm, day alarm

and weekday alarm registers are all coded in BCD format.

When one of the RTC counters is read (memory locations 02h through 08h), the contents of all counters are frozen

at the beginning of a read cycle. Therefore, faulty reading of the clock / calendar during a carry condition is

prevented.

6.1. CLKOUT OUTPUT

A programmable square wave is available at the CLKOUT pin. Frequencies of 32.768 kHz, 1024 Hz, 32 Hz and 1

Hz can be generated for use as system clock, microcontroller clock or input to a charge pump. CLKOUT is a CMOS

push-pull output, and if disabled it becomes logic 0.

7. DEVICE PROTECTION DIAGRAM

INT

V

SS

SDA

SCL

CLKOUT

V

DD

CLKOE