PCF8563 datasheet(16/45 Pages) NXP

16 / 45 page

PCF8563

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Product data sheet

Rev. 9 — 16 June 2011

16 of 45

NXP Semiconductors

PCF8563

Real-time clock/calendar

[1]

Default value.

8.8 Timer function

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 (4096 Hz, 64 Hz, 1 Hz, or 1⁄60 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. The TF may only be cleared by using the interface. 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.

8.8.1 Register Timer_control

[1]

Default value.

[2]

These bits determine the source clock for the countdown timer; when not in use, TD[1:0] should be set to

1⁄60 Hz for power saving.

Table 22.

CLKOUT_control - CLKOUT control register (address 0Dh) bit description

Bit

Symbol

Value

Description

the CLKOUT output is inhibited and CLKOUT output is

set to logic 0

1[1]

the CLKOUT output is activated

6 to 2 -

unused

1 to 0 FD[1:0]

frequency output at pin CLKOUT

00[1]

32.768 kHz

1.024 kHz

32 Hz

1 Hz

Table 23.

Timer_control - timer control register (address 0Eh) bit description

Bit

Symbol

Value

Description

7TE

0[1]

timer is disabled

timer is enabled

6 to 2 -

unused

1 to 0 TD[1:0]

timer source clock frequency select[2]

4.096 kHz

64 Hz

1 Hz

11[2]

1⁄60 Hz

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