Introduction to RTC in n3292 Series

Introduction to RTC in n3292 Series

1 RTC features

? Has time counters (seconds, minutes, hours) and calendar counters, used to calculate the time

? Absolute timing function (seconds, minutes, hours, days, months, and years)

? Relative timing Function

? Supports 12-hour/24-hour Mode

? Automatically recognize a leap year

? Weekly counter

? Frequency Calibration

? Supports the clock drop interrupt function

? Supports the wake-up function.

Power-down wake-up function

Suspend wake-up function

2 RTC function introduction 2.1 RTC Initialization

When the RTC is powered on, the software needs to write a key value (0xa5eb1357) to the inir register to reset the RTC.

? After the RTC is powered on, you only need to initialize the RTC once. (This operation has been done in the IBR of n3292)

? The software can obtain the RTC status information by reading the inir value.

2 bit 0: RTC initialization status

2 bit 1: Level Shift enabling status

Note:Even if you only use rtcYou must also press the powerkeyTo enable level shift.

2.2 Register Access

Register read/write password-0xa965

2. The software can read the bit 16 (ENF) of AER to determine whether the RTC register can be accessed.

2. Access to RTC can be disabled by writing a password-not value to AER.

2. After each write operation on the RTC register, you must wait until the reg_flag position is 1 before you can write the RTC register.

2.3 RTC Calibration

RTC calibration function: When the 32 K crystal oscillator is not punctual, the calibration function is used to calibrate the RTC counter.

2 The RTC engine uses the APB clock to sample the RC oscillator clock.

2 The user needs to use the external crystal oscillator and the internal RC Shock Calibration counter (osc_32k_cnt) to calculate the FCR calibration value.

Calculation formula:

Rtc_1hz_cnt is used to calculate the RTC clock.

RTC-_ clock_rate = (pclk/rtc_1hz_cnt) * 32768

Fcr_int = RTC-_ clock_rate integer part-1

Fcr_frac = RTC-_ clock_rate decimal part * 60-1

For example:

Assume that rtc_1hz_cnt = 50103132

Rtc_clock_rate = (500000/50103132) * 32768 = 32700.5505

Fcr_int= 32699

Fcr_frac = 0.5505*60-1 = 32

2.4 Time and calendar

CLR: Calendar register

Tar: Time Register

2.5 time and calendar alarms

? Car: Calendar alarm register

Year shield/month shield/day shield/week Shield

? Tar: Time Alarm register

Time Blocking/minute blocking/second Blocking

2.6 24-hour/12-hour Mode Selection

Bit0 of the tssr register:

U 1: 24-hour Mode

Ü 0: 12-hour Mode

2.7 weeks and leap years

? RTC supports the week function DWR

? RTC supports the leap year Indication Function LIR

Ü years (read-only)

Ü note:

Do not check the date condition when setting the RTC time

For example, if the current date is 2009 and you want to set the date

Lir indicates a leap year from time to time. 2/29 is invalid

However, 2012 is a leap year, And 2/29 is legal.

2.8 RTC clock drops

The clock drops are used to request an interruption (TTR)

The interrupt cycle can be: 1/128 S, 1/64 s, 1/32 s, 1/16 s, 1/8 s, 1/4S, 1/2 s and 1 s

2.9 interrupt enable and interrupt Status Register (rier/riir)

Ü alarm interruption (absolute)

Alarm_en (pwron [3]) must be enabled

When CLR = car and LR = tar, the RTC alarm is interrupted.

Ü time drop interruption

Ü power switch interruption

Ü alarm interruption (relative)

Rel_alarm_en (pwron [4]) must be enabled

When relative_time [11: 0] is set, the internal counter starts counting from 0. When the Count reaches relative_time [11: 0], the RTC timed alarm is interrupted (relative)

Ü after the system is powered off, the interruption status will not be maintained

2.10 registers for software use

RTC provides two 32-bit registers for software use.

Ü when only RTC is powered, the value of the Register remains unchanged. (Dummy0/dummy1)

3 Power Control Function 3.1 RTC power control supports power-on and power-off Functions

? Start

Power key boot

Start RTC alarm

? Shutdown

2. Hardware Shutdown

Even if the software crashes, you can press the power key for a certain period of time to shut down the system.

2 software shutdown

When the software detects that the power key is pressed, the software can shut down

3.2 Definitions

2 power key (pwrkey)

Keys used by pwrkey to switch on/off the server

2 power control signal (pwce)

Pwce is the control signal of the control power supply part.

2 power key status (pwr_key)

2 software status (sw_status)

RTC provides 8-bit data to store software information.

2 hardware shutdown enabling (hw_pclr_en)

RTC provides the hardware shutdown function, which can be turned off even if the software crashes.

This one is used to enable the hardware shutdown Function

2 Power Control Signal Delay Time (power_key_duration_length)

At least the press time is required for power keys during system startup.

Minimum powerkey press time = 0.25 * (power_key_duartion + 1) seconds

2 power key trigger mode

L edge triggering

When the RTC is powered on, press the power key to exceed the delay time, and then open

L Level Trigger

When the RTC is powered on, pressing the power key exceeds the delay.

2. Hardware shutdown time (pclr_time)

If you press the power key longer than this time, the system will shut down

2 power on (pwr_on)

This bit is used to control pwce to control the power supply of the system.

Ü when the power key is pressed, The pwce will change from 0 to 1.

Ü when the power key is not pressed, pwce changes from 1 to 0.

2 power-down mode

Power off all except rtc

2. Interruption enabling and interruption status

Ü RTC provides four interruptions (the interrupted state cannot be maintained when the power is down)

Ü alarm interruption (aier/AI and raier/RAI)

Ü time drop interruption (Tier and Ti)

Ü power switch interruption (pswier and pswi)

Indicates that the power key has been pressed.

3.3 system boot control process

? Start with power key

2. When the user presses the power key, the power control signal pwce is set to high.

2. After the pwr_on bit is set, the pwce can remain unchanged. In this case, the power key can be opened. When the system powers on, IBR first sets the pwr_on bit to lock pwce.

2 If the pwr_on bit is not set to 1, pwce will return to the low level when the power key is released

2 RTC provides a function to delay the pwce signal, so that the changes in the pwce signal relative to the power key have a delay time (power_key_duration_length)

Minimum time that the power key must be pressed at startup

Minimum power key retention time = 0.25 * (power_key_duration + 1) seconds

? Started through RTC alarm

2 in power-down mode, if RTC alarm occurs, RTC sets pwce to high by holding an internal alarm_hold signal.

2. After pwr_on is set, the alarm_hold signal is cleared and pwr_on maintains the pwce signal. When the system is started, IBR will first set pwr_on

3.4 system shutdown control process

? Software shutdown

2. If you cannot figure out the power key to shut down, you can clear the pwr_on bit at any time. For example, Timed Shutdown

? Strong hardware Shutdown

2 RTC provides a strong hardware shutdown function. you can disable the system even if the software crashes.

2. When the hardware strong shutdown function (hw_pclr_en) is enabled, the system will be shut down by pressing the powerkey for a certain period of time.

3.3 example of system switch control

? Normal Shutdown Process

2. After a user receives a power switch interruption, the user can decide whether to execute the shutdown process.

2. If you want to perform the shutdown process, you only need to set sw_pclr to immediately shut down the system.

? Shutdown Process when software is busy/crashed

2. Assume that the hardware shutdown time is set to 6 seconds.

2. The software can decide whether to execute the shutdown process within 3 seconds.

2. If the software does not execute the shutdown process, the hardware will be shut down in 1 second.

Introduction to RTC in n3292 Series