pcf8564a NXP Semiconductors, pcf8564a Datasheet - Page 16

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

NXP Semiconductors
PCF8564A_1
Product data sheet
8.8.1 Register Timer_ctrl
8.8 Timer function
Table 22.
[1]
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 TF (Timer Flag) to logic 1. The TF may only be cleared using the
interface.
The generation of interrupts from the timer function is controlled via bit TIE. If bit TIE is
enabled the INT pin follows the condition of bit TF. The interrupt may be generated as a
pulsed signal every countdown period or as a permanently active signal which follows the
condition of the timer flag TF. TI_TP is used for this mode control. When reading the timer,
the current countdown value is returned.
Table 23.
[1]
[2]
Bit
7
6 to 2 -
1 to 0 FD[1:0]
Bit
7
6 to 2 -
1 to 0 TD[1:0]
Default value.
Default value.
These bits determine the source clock for the countdown timer; when not in use, TD[1:0] should be set to
1
60
Symbol
FE
Symbol
TE
Hz for power saving.
CLKOUT_ctrl - CLKOUT control register (address 0Dh) bit description
Timer_ctrl - timer control register (address 0Eh) bit description
Rev. 1 — 8 October 2009
Value
0
1
-
00
01
10
11
Value
0
1
-
00
01
10
11
[1]
[1]
[1]
[2]
1
Description
the CLKOUT output is inhibited and CLKOUT output is
set to logic 0
the CLKOUT output is activated
unused
frequency output at pin CLKOUT
Description
timer is disabled
timer is enabled
unused
timer source clock frequency select
60
32.768 kHz
1.024 kHz
32 Hz
1 Hz
4.096 kHz
64 Hz
1 Hz
1
Hz) and enables or disables the timer. The timer
60
Hz
Real time clock and calendar
PCF8564A
[2]
© NXP B.V. 2009. All rights reserved.
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