PCF212311 View Datasheet(PDF) - NXP Semiconductors.
Part Name
Description
MFG CO.
'PCF212311' PDF : 63 Pages View PDF
NXP Semiconductors
PCF2123
SPI Real time clock/calendar
8.7.1 Minute and second interrupts
The pulse generator for the minute and second interrupt operates from an internal 64 Hz
clock and consequently generates a pulse of 1⁄64 second in duration.
If the MSF flag is cleared before the end of the INT pulse, then the INT pulse is shortened.
This allows the source of a system interrupt to be cleared immediately it is serviced, i.e.,
the system does not have to wait for the completion of the pulse before continuing; see
Figure 17. Instructions for clearing MSF are given in Section 8.6.5.
seconds counter 58 59
MSF
INT
SCL
instruction
(1)
8th clock
CLEAR INSTRUCTION
001aaf908
(1) Indicates normal duration of INT pulse (bit TI_TP = 1)
Fig 17. Example of shortening the INT pulse by clearing the MSF flag
The timing shown for clearing bit MSF in Figure 17 is also valid for the non-pulsed
interrupt mode i.e. when bit TI_TP = 0, INT may be shortened by setting both MI and SI or
MSF to logic 0.
8.7.2 Countdown timer interrupts
The generation of interrupts from the countdown timer is controlled via bit TIE.
The pulse generator for the countdown timer interrupt also uses an internal clock, but this
time it is dependent on the selected source clock for the countdown timer and on the
countdown value n. As a consequence, the width of the interrupt pulse varies (see
Table 34).
Table 34. INT operation (bit TI_TP = 1)
Source clock (Hz)
INT period (s)
n = 1[1]
4096
64
1
1⁄60
1⁄8192
1⁄128
1⁄64
1⁄64
[1] n = loaded countdown value. Timer stopped when n = 0.
n>1
1⁄4096
1⁄64
1⁄64
1⁄64
If the TF flag is cleared before the end of the INT pulse, then the INT pulse is shortened.
This allows the source of a system interrupt to be cleared immediately it is serviced, i.e.,
the system does not have to wait for the completion of the pulse before continuing (see
Figure 18). Instructions for clearing MSF can be found in Section 8.6.5.
PCF2123
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 April 2011
© NXP B.V. 2011. All rights reserved.
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