32-Bit Arm ®

HT32F5828

Cortex ® -M0+ MCU

27

Real Time Clock (RTC)

Introduction

The Real Time Clock, RTC, circuitry includes the APB interface, a 24-bit up-counter, a control register, a prescaler, a compare register and a status register. Most of the RTC circuits are located in the V

DD

Power Domain, as shown in dotted red box in the accompanying figure, except for the APB interface. The APB interface is located in the V

DD15

domain. Therefore, it is necessary to be isolated by the ISO signal that comes from the power control unit when the V

DD15

domain is powered off, i.e., when the device enters the Power-Down mode. The RTC counter is used as a wakeup timer to let the system resume from the power-saving modes. The detailed RTC function will be described in the following sections.

LSE

OSC

CK_LSE

1

LSI RC

OSC

CK_LSI

0

RTCSRC

CK_RTC

ISO

APB Bus

APB Interface and

ISO & Level Shift

Prescaler

CK_SECOND

24-bit Counter

CMPCLR

Compare

Register

24

Match

24

V

DD

Power Domain V

DD

1.5 V Core Power Domain V

DD15 set

CSECFLAG set set

OVFLAG

CMFLAG

Figure 197. RTC Block Diagram

CSECIEN

OVIEN

CMIEN

CSECWEN

OVWEN

CMWEN

RTCINT

( To NVIC )

RTCWAKEUP

( To EXTI and PWRCU )

Features

▆

24-bit up-counter for counting elapsed time

▆

▆

▆

▆

▆

Programmable clock prescaler

● Division factor: 1, 2, 4, 8…, 32768

24-bit compare register for alarm usage

RTC clock source

● LSE oscillator clock

● LSI oscillator clock

Three RTC Interrupt/wakeup settings

● RTC second clock interrupt/wakeup

● RTC compare match interrupt/wakeup

● RTC counter overflow interrupt/wakeup

The RTC interrupt/wakeup event can work together with power management to wake up the chip from power saving mode

Rev. 1.00 562 of 637 December 28, 2020