PCF8523 NXP [NXP Semiconductors], PCF8523 Datasheet - Page 34

• Manufacturer Part Number: PCF8523
• Description: Real-Time Clock (RTC) and calendar
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCF8523
Product data sheet
8.9.2.2 Countdown timer function
WTAF is read only. A read of the register Control_2 (01h) will automatically reset WTAF
(WTAF = 0) and clear the interrupt.
When configured as a countdown timer (TAC[1:0] = 01), timer A counts down from the
software programmed 8-bit binary value n in register Tmr_A_reg (11h). When the counter
reaches 1, the following events occur on the next rising edge of the timer clock (see
Figure
Fig 18. Watchdog activates an interrupt when timed out
•
•
•
•
•
timer value
The watchdog timer stops.
The countdown timer flag CTAF (register Control_2) is set logic 1.
When the interrupt generation is enabled (CTAIE = 1) an interrupt signal on INT1 will
be generated.
The counter automatically reloads.
The next timer-period starts.
watchdog
WTAF
19):
INT1
TAC[1:0] = 10, WTAIE = 1, WTAF = 1, an interrupt is generated.
n = 1
All information provided in this document is subject to legal disclaimers.
Rev. 3 — 30 March 2011
n = 0
Real-Time Clock (RTC) and calendar
PCF8523
© NXP B.V. 2011. All rights reserved.
MCU
n
013aaa327
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