MFS2301BMBACEP datasheet(61/230 Pages) NXP

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NXP Semiconductors

FS23

Safety system basis chip (SBC) with power management, CAN FD and LIN transceivers

17 Long duration timer

The FS23 features a long duration timer (LDT). The timer is configurable by SPI/I2C and can operate in Normal

and in Low-Power modes.

The FS23 provides several functions and offers a wide range of configurable counting periods, as well as a

calibration mechanism for oscillator compensation.

The timer can be activated in Normal mode and all prescaler options can be selected to allow timer circuitry

verification.

The timer is based on a 24-bit counter, with a 1 MHz/64-input clock, allowing a 1.0 second time base.

aaa-052150

CONTROL REGISTER

To EXTERNAL

To internal:

mode change

(LPON, LPOFF, WU)

INTB

READ REGISTER(S)

24-bit COUNTER

COMP.

24 bits: WAKE UP REGISTER

16 bits: AFTER RUN

PRESCALER 2

(/15625)

PRESCALER 1

(/64)

PRESCALER 3

(/2)

SPI/I2C

interface

1 MHz

OSC

1 µs

64 µs

128 µs

1.0 s

1.0 s (cal:128 µs)

(calibration)

Figure 33. Long duration timer block diagram

In Normal mode operation, the timer can count up to 194 days, with 1 second resolution. In Calibration mode,

the prescaler 2 is bypassed and the timer can count up to 36 minutes, with 128 µs resolution.

Mode

Input clock

frequency

Input clock

period

Prescaler

Counter resolution

Max count

Operation

1 MHz

1 µs

64 x 15625

1.0 s

4660 Hrs

194 days

Calibration

1 MHz

1 µs

64 x 2

128 µs

2160 s

36 min

Table 29. Long duration timer characteristics

The LDT has two modes of operation based on the prescaler used during the count.

• When LDT_MODE = 0, the LDT is set in long count mode.

• When LDT_MODE = 1, the LDT is set in short count mode.

The LDT_AFTER_RUN[15:0] bits are used to set or to read the after-run target value in Normal mode.

The LDT_WUP_H[7:0] and the LDT_WUP_L[15:0] bits is used to set or to read the wakeup target value, in

combination with the LDT_SEL bit:

• LDT_WUP_H[7:0] contains the eight most significant bits of the wake-up target value.

• LDT_WUP_L[15:0] contains the 16 least significant bits of the wake-up target value.

FS23

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 7.0 — 16 October 2024

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