ST10F269-Q3 datasheet(102/160 Pages) STMICROELECTRONICS

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When RTCD increments to reach 00000h, The 20-bit word stored into RTCPH, RTCPL registers is loaded

in RTCD.

Bit 15 to bit 4 of RTCPH and RTCDH are not used. When reading, the return value of those bit will be

zeros.

16.1.4 - RTCH & RTCL: RTC Programmable COUNTER Registers

The RTC has 2 x 16-bit programmable counters which count rate is based on the basic time reference (for

example 1 second). As the clock oscillator may be kept working, even in power down mode, the RTC

counters may be used as a system clock. In addition RTC counters and registers are not modified at any

system reset. The only way to force their value is to write them via the XBUS.

Those counters are write protected as well. The bit RTOFF of the RTCCON register must be set (RTC

dividers and counters are stopped) to enable a write operation on RTCH or RTCL.

A write operation on RTCH or RTCL register loads directly the corresponding counter. When reading, the

current value in the counter (system date) is returned.

The counters keeps on running while the clock oscillator is working.

RTCL (EC0Eh)

XBUS

Reset Value: XXXXh

RTCH (EC10h)

XBUS

Reset Value: XXXXh

Note: Those registers are nor reset

Figure 53 : DIVIDER Counters

9876543210

RTCL

9876543210

RTCH

11 10 9

15 14 13 12

RTCDH

RTCDL

11 10 9

15 14 13 12

19 18 17 16

20 bit word internal value of the prescalar divider

ST10F269-Q3 Datasheet(PDF) 102 Page - STMicroelectronics