Datasheet

Product data sheet Rev. 4 — 5 December 2014 15 of 48

NXP Semiconductors

PCA8565

Real time clock/calendar

8.6.3 Register Day_alarm

[1] Default value.

8.6.4 Register Weekday_alarm

[1] Default value.

8.7 Timer functions

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

⁄

Hz) and enables or disables the timer. The timer

counts down from a software-loaded 8-bit binary value. At the end of every countdown,

the timer sets the timer flag (TF) in the register Control_status_2. The TF may only be

cleared by command. The asserted TF can be used to generate an interrupt (on pin INT

The interrupt may be generated as a pulsed signal every countdown period or as a

permanently active signal which follows the state of TF. Bit TI_TP is used to control this

mode selection. When reading the timer, the current countdown value is returned.

8.7.1 Register Timer_control

The timer register is an 8-bit binary countdown timer. It is enabled and disabled via the

bit TE in register Timer_control. The source clock for the timer is also selected by the

TD[1:0] in register Timer_control. Other timer properties such as interrupt generation are

controlled via register Control_2.

Table 21. Register Day_alarm (address 0Bh) bits description

Bit Symbol Value Place value Description

7 AE_D 0 - day alarm is enabled

[1]

- day alarm is disabled

6 - - - unused

5 to 4 DAY_ALARM 0 to 3 ten’s place day alarm information coded in BCD

format

3 to 0 0 to 9 unit place

Table 22. Register Weekday_alarm (address 0Ch) bits description

Bit Symbol Value Description

7 AE_W 0 weekday alarm is enabled

[1]

weekday alarm is disabled

6 to 3 - - unused

2 to 0 WEEKDAY_ALARM 0 to 6 weekday alarm information coded in BCD format