pcf2129a NXP Semiconductors, pcf2129a Datasheet - Page 20

• Manufacturer Part Number: pcf2129a
• Description: Integrated Rtc, Tcxo And Quartz Crystal
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF2129A_1
Product data sheet
8.7.1 Power-On Reset (POR)
8.7.2 Power-On Reset Override (PORO)
8.7 Reset function
The PCF2129A has a Power-On Reset (POR) and a Power-On Reset Override (PORO)
function implemented.
The POR is active whenever the oscillator is stopped. The oscillator is also considered to
be stopped during the time between power-on and stable crystal resonance (see
Figure
supply voltage. Whenever an internal reset occurs, the oscillator stop flag is set (OSF set
logic 1).
After POR, the following mode is entered:
The register values after power-on are shown in
The POR duration is directly related to the crystal oscillator start-up time. Due to the long
start-up times experienced by these types of circuits, a mechanism has been built in to
disable the POR and hence speed up on-board test of the device.
Fig 10. Dependency between POR and oscillator
Fig 11. Power-On Reset (POR) system
•
•
•
•
•
32.768 kHz CLKOUT active
Power-On Reset Override (PORO) available to be set
24 hour mode is selected
Battery switch-over is enabled
Battery low detection is enabled
10). This time may be in the range of 200 ms to 2 s depending on temperature and
oscillation
internal
reset
V
DD
SDA/CE
SCL
Rev. 01 — 13 January 2010
OSCILLATOR
POR_OVRD
OVERRIDE
RESET
CLEAR
chip in reset
0 = override inactive
1 = override active
0 = clear override mode
1 = override possible
0 = stopped, 1 = running
osc stopped
Integrated RTC, TCXO and quartz crystal
Table
4.
chip not in reset
001aaj324
reset
PCF2129A
© NXP B.V. 2010. All rights reserved.
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