pcf2127a NXP Semiconductors, pcf2127a Datasheet - Page 41

• Manufacturer Part Number: pcf2127a
• Description: Integrated Rtc, Tcxo And Quartz Crystal
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF2127A_1
Product data sheet
8.12.1 Timestamp flag
8.12 Timestamp function
The PCF2127A has an active LOW timestamp input pin TS, internally pulled with an
on-chip pull-up resistor to the internal power supply of the device. It also has a timestamp
detection circuit which can detect two different events:
The timestamp function is enabled by default after power-on and it can be switched off by
setting the control bit TSOFF (register Timestp_ctl).
A most common application of the timestamp function is described in
See
1. TS input on the pin is driven to an intermediate level between the power supply and
2. TS input on the pin is driven to ground.
1. When the TS input pin is driven to an intermediate level between the power supply
2. When the TS input pin is driven to ground the following sequence occurs:
Fig 24. Timestamp detection with two push-buttons on one the TS pin (e.g. for tamper
ground.
and ground the following sequence occurs:
a. The actual date and time are stored in the timestamp registers.
b. The timestamp flag TSF1 (register Control_1) is set.
c. If the TSIE bit (register Control_2) is active, an interrupt on the INT pin is
The TSF1 flag can be cleared by using the interface. Clearing the flag will clear the
interrupt. Once TSF1 is cleared it will only be set again when a new negative edge on
TS is detected.
a. The actual date and time are stored in the timestamp registers.
b. In addition to the TSF1 flag the TSF2 flag (register Control_3) is set.
c. If the TSIE bit is active, an interrupt on the INT pin is generated.
Section 8.13.5
generated.
detection)
push-button 2
connected to
cover 2
for a description of interrupt generation from the timestamp function.
Rev. 01 — 21 January 2010
V
SS
R2 =
200 kΩ
± 5 %
Integrated RTC, TCXO and quartz crystal
push-button 1
connected to
cover 1
TS
1
2
3
4
5
6
7
8
PCF212xA
V
DD
R1 =
200 kΩ
± 20 %
013aaa176
PCF2127A
16
15
14
13
12
11
10
9
Ref. 3
© NXP B.V. 2010. All rights reserved.
“AN10857”.
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