pcf8564a NXP Semiconductors, pcf8564a Datasheet - Page 8

• Manufacturer Part Number: pcf8564a
• Description: Real Time Clock And Calendar
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF8564A_1
Product data sheet
Fig 4.
COUNTDOWN COUNTER
When bits TIE and AIE are disabled, pin INT will remain high-impedance.
Interrupt scheme
8.3.2.1 Interrupt output
TE
Bits TF and AF:
countdown, TF is set to 1. These bits maintain their value until overwritten using the
interface. If both timer and alarm interrupts are required in the application, the source of
the interrupt can be determined by reading these bits. To prevent one flag being
overwritten while clearing another, a logic AND is performed during a write access.
Bits TIE and AIE:
TF or AF is asserted respectively. The interrupt is the logical OR of these two conditions
when both AIE and TIE are set.
Countdown timer interrupts:
uses an internal clock and is dependent on the selected source clock for the countdown
timer and on the countdown value n. As a consequence, the width of the interrupt pulse
varies (see
Table 7.
[1]
[2]
Source clock (Hz)
4096
64
1
1
60
from interface:
from interface:
TF and INT become active simultaneously.
n = loaded countdown value. Timer is stopped when n = 0.
set alarm
clear AF
clear TF
flag, AF
INT operation (bit TI_TP = 1)
Table
When an alarm occurs, AF is set to 1. Similarly, at the end of a timer
SET
SET
7).
These bits activate or deactivate the generation of an interrupt when
AF: ALARM
TF: TIMER
CLEAR
CLEAR
FLAG
Rev. 1 — 8 October 2009
The pulse generator for the countdown timer interrupt
INT period (s)
n = 1
1
1
1
1
TRIGGER
8192
128
64
64
GENERATOR 2
[2]
CLEAR
PULSE
[1]
to interface:
read TF
to interface:
read AF
TI_TP
0
1
Real time clock and calendar
n > 1
1
1
1
1
AIE
TIE
4096
64
64
64
PCF8564A
013aaa087
© NXP B.V. 2009. All rights reserved.
E.G.AIE
INT
0
1
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