PCF8523 NXP [NXP Semiconductors], PCF8523 Datasheet - Page 30

• Manufacturer Part Number: PCF8523
• Description: Real-Time Clock (RTC) and calendar
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCF8523
Product data sheet
8.9.1.1 Register Tmr_CLKOUT_ctrl and clock output
8.9.1 Timer registers
8.9 Timer function
The PCF8523 has three timers:
Timer A and timer B both have five selectable source clocks allowing for countdown
periods from less than 1 ms to 255 h. To control the timer functions and timer output, the
registers 01h, 0Fh, 10h, 11h, 12h, and 13h are used.
Table 32.
[1]
CLKOUT frequency selection:
the Tmr_CLKOUT_ctrl register. Frequencies of 32.768 kHz (default) down to 1 Hz can be
generated (see
charge pump, or for calibration of the oscillator.
Bit
7
6
5 to 3
2 to 1
0
•
•
•
Timer A can be used as a watchdog timer or a countdown timer (see
can be configured by using TAC[1:0] in the Tmr_CLKOUT_ctrl register (0Fh).
Timer B can be used as a countdown timer (see
by using TBC in the Tmr_CLKOUT_ctrl register (0Fh).
Second interrupt timer is used to generate an interrupt once per second (see
Section
Default value.
Symbol
TAM
TBM
COF[2:0]
TAC[1:0]
TBC
Tmr_CLKOUT_ctrl - timer and CLKOUT control register (address 0Fh) bit
description
8.9.4).
All information provided in this document is subject to legal disclaimers.
Table
33) for use as a system clock, microcontroller clock, input to a
Rev. 3 — 30 March 2011
Value
0
1
0
1
see
00
01
10
0
1
[1]
[1]
[1]
Clock output operation is controlled by the COF[2:0] in
[1]
Table 33
to 11
Description
permanent active interrupt for timer A and for
the second interrupt timer
pulsed interrupt for timer A and the second
interrupt timer
permanent active interrupt for timer B
pulsed interrupt for timer B
CLKOUT frequency selection
timer A is disabled
timer A is configured as countdown timer
timer A is configured as watchdog timer
timer B is disabled
timer B is enabled
if CTAIE (register Control_2) is set logic 1, the
interrupt is activated when the countdown
timed out
if WTAIE (register Control_2) is set logic 1,
the interrupt is activated when timed out
if CTBIE (register Control_2) is set logic 1, the
interrupt is activated when the countdown
timed out
Real-Time Clock (RTC) and calendar
Section
8.9.3). It can be configured
PCF8523
© NXP B.V. 2011. All rights reserved.
Section
8.9.2). It
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