Datasheet

PCF8523 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 6 — 17 September 2013 34 of 78
NXP Semiconductors
PCF8523
Real-Time Clock (RTC) and calendar
8.9.1.5 Register Tmr_B_freq_ctrl
[1] Default value.
8.9.1.6 Register Tmr_B_reg
[1] Timer period in seconds: where T_B is the countdown value.
8.9.1.7 Programmable timer characteristics
Table 38. Tmr_B_freq_ctrl - timer B frequency control register (address 12h) bit
description
Bit Symbol Value Description
7 - - unused
6 to 4 TBW[2:0] low pulse width for pulsed timer B interrupt
000
[1]
46.875 ms
001 62.500 ms
010 78.125 ms
011 93.750 ms
100 125.000 ms
101 156.250 ms
110 187.500 ms
111 218.750 ms
3 - - unused
2 to 0 TBQ[2:0] source clock for timer B (see Table 40
)
000 4.096 kHz
001 64 Hz
010 1 Hz
011
1
⁄
60
Hz
111
[1]
110
100
1
⁄
3600
Hz
Table 39. Tmr_B_reg - timer B value register (address 13h) bit description
Bit Symbol Value Description
7 to 0 T_B[7:0] 00 to FF
timer value
[1]
timerperiod
T_B
SourceClockFrequency
---------------------------------------------------------------
=
Table 40. Programmable timer characteristics
TAQ[2:0]
TBQ[2:0]
Timer source
clock frequency
Units Minimum
timer-period
(T_x = 1)
Units Maximum
timer-period
(T_x = 255)
Units
000 4.096 kHz 244 s 62.256 ms
001 64 Hz 15.625 ms 3.984 s
010 1 Hz 1 s 255 s
011
1
⁄
60
Hz 1 min 255 min
111
110
100
1
⁄
3600
Hz 1 hour 255 hour