PCA8565BS NXP [NXP Semiconductors], PCA8565BS Datasheet - Page 14

• Manufacturer Part Number: PCA8565BS
• Description: Real time clock/calendar
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCA8565_2
Product data sheet
9.7 Timer functions
Alarm registers which have their bit AE_x at logic 1 are ignored.
Table 23
flags is made by a write command; therefore bits 7, 6, 4, 1 and 0 must be written with their
previous values. Repeatedly re-writing these bits has no influence on the functional
behavior.
To prevent the timer flags being overwritten while clearing AF, a logical AND is performed
during a write access. Writing a logic 1 will cause the flag to maintain its value, whereas
writing a logic 0 will cause the flag to be reset.
Table 22.
The following table shows what instruction must be sent to clear bit AF. In this example bit
TF is unaffected.
Table 23.
The 8-bit countdown timer at address 0Fh is controlled by the timer control register at
address 0Eh. The timer control register determines one of 4 source clock frequencies for
the timer (4.096 kHz, 64 Hz, 1 Hz, or
counts down from a software-loaded 8-bit binary value. At the end of every countdown,
the timer sets the timer flag (TF). The TF is cleared using the interface. The asserted TF is
used to generate an interrupt (INT). The interrupt is generated as a pulsed signal every
countdown period or as a permanently active signal which follows the condition of TF.
Bit TI_TP is used to control this mode selection. When reading the timer, the actual
countdown value is returned.
Register
Control_2
Register
Control_2
Fig 7.
shows an example for clearing bit AF but leaving bit TF unaffected. Clearing the
Example where only the minute alarm is used and no other interrupts are enabled.
AF timing
Flag location in register Control_2
Example to clear only AF (bit 3) in register Control_2
Bit
7
-
Bit
7
-
INT when AIE = 1
minutes counter
minute alarm
Rev. 02 — 16 June 2009
6
-
6
-
AF
44
45
5
-
5
-
1
60
Hz) and enables or disables the timer. The timer
4
-
4
-
45
3
AF
3
0
2
TF
2
1
Real time clock/calendar
001aaf903
PCA8565
46
© NXP B.V. 2009. All rights reserved.
1
-
1
-
0
-
0
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