Datasheet

PCF8523 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 6 — 17 September 2013 31 of 78
NXP Semiconductors
PCF8523
Real-Time Clock (RTC) and calendar
8.9 Timer function
The PCF8523 has three timers:
• Timer A can be used as a watchdog timer or a countdown timer (see Section 8.9.2). It
can be configured by using TAC[1:0] in the Tmr_CLKOUT_ctrl register (0Fh)
• Timer B can be used as a countdown timer (see Section 8.9.3). It can be configured
by using TBC in the Tmr_CLKOUT_ctrl register (0Fh)
• Second interrupt timer is used to generate an interrupt once per second (see
Section 8.9.4
)
Timer A and timer B both have five selectable source clocks allowing for countdown
periods from less than 1 ms to 255 h. To control the timer functions and timer output, the
registers 01h, 0Fh, 10h, 11h, 12h, and 13h are used.
Fig 18. Offset calibration calculation workflow
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