PCF8563
APPLICATION SUMMARY
The PCF8563 contains sixteen 8-bit registers with an auto-incrementing address register, an
on-chip 32.768 kHz oscillator with an integrated capacitor, a frequency divider which
provides the source clock for the Real-Time Clock (RTC), a programmable clock output, a
timer, an alarm, a voltage-low detector and a 400 kHz I 2 C-bus interface.
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, Months, Years as well as the Minute alarm, Hour alarm
and Day alarm registers are all coded in BCD format. The Weekdays and Weekday alarm
register are not coded in BCD format.
When one of the RTC registers is read the contents of all counters are frozen. Therefore,
faulty reading of the clock/calendar during a carry condition is prevented.
Alarm function modes
By clearing the MSB (bit AE = Alarm Enable) of one or more of the alarm registers, the
corresponding alarm condition(s) will be active. In this way an alarm can be generated from
once per minute up to once per week. The alarm condition sets the alarm flag, AF (bit 3 of
Control/Status 2 register). The asserted AF can be used to generate an interrupt (INT). Bit
AF can only be cleared by software.
Timer
The 8-bit countdown timer (address 0FH) is controlled by the Timer Control register
(address 0EH). The Timer Control register selects one of 4 source clock frequencies for the
timer (4096, 64, 1, or 1/60 Hz), and enables/disables the timer. The timer counts down from
a software-loaded 8-bit binary value. At the end of every countdown, the timer sets the
timer flag TF. The timer flag TF can only be cleared by software. The asserted timer flag
TF can be used to generate an interrupt (INT). The interrupt may be generated as a pulsed
signal every countdown period or as a permanently active signal which follows the
condition of TF. TI/TP is used to control this mode selection. When reading the timer, the
current countdown value is returned.
8/23
TGS [ Tiger Electronic Co.,Ltd ]
