NRF52811-QCAA-R datasheet(252/444 Pages) NORDIC

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Peripherals

The following is a summary of the jitter introduced on tasks and events. Figures illustrating jitter follow.

Task

Delay

CLEAR, STOP, START, TRIGOVRFLOW

+15 to 46 μs

Table 73: RTC jitter magnitudes on tasks

Operation/Function

Jitter

START to COUNTER increment

+/- 15 μs

COMPARE to COMPARE 20

+/- 62.5 ns

Table 74: RTC jitter magnitudes on events

1. CLEAR and STOP (and TRIGOVRFLW; not shown) will be delayed as long as it takes for the peripheral to

clock a falling edge and rising of the LFCLK. This is between 15.2585 μs and 45.7755 μs – rounded to 15

μs and 46 μs for the remainder of the section.

0x000

SysClk

LFClk

PRESC

COUNTER

CLEARa

X+1

0x000000

0x000001

0 or more SysClk after

CLEAR

CLEARb

1 or more SysClk before

<= ~46 us

>= ~15 us

Figure 99: Timing diagram - DELAY_CLEAR

SysClk

LFClk

PRESC

COUNTER

STOPa

X+1

0 or more SysClk after

STOP

STOPb

1 or more SysClk before

<= ~46 us

>= ~15 us

0x000

Figure 100: Timing diagram - DELAY_STOP

2. The START task will start the RTC. Assuming that the LFCLK was previously running and stable, the

first increment of COUNTER (and instance of TICK event) will be typically after 30.5 μs +/-15 μs. In

some cases, in particular if the RTC is STARTed before the LFCLK is running, that timing can be up to

~250 μs. The software should therefore wait for the first TICK if it has to make sure the RTC is running.

20 Assumes RTC runs continuously between these events.

Note: 32.768 kHz clock jitter is additional to the numbers provided above.

4454_140 v1.0

252

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