Method for achieving accurate clock timing by arranging RTC (real time clock) in MCU (micro control unit)

Abstract

The invention discloses a method for achieving accurate clock timing by arranging an RTC (real time clock) in an MCU (micro control unit). The method comprises the following steps: (1) adjustment of a prescaler: setting the default value of the prescaler as (k-1) when a kHZ crystal oscillator is utilized, and generating one second pulse interruption when the counting of the prescaler is k; (2) adjustment of a clock calibration register: utilizing a temperature sensor to collect the external temperature in a fixed time window, looking for the value of frequency offset according to the temperature, calculating the number of the actual frequency offset PPM (percent per million), and calculating the value of the calibration register; (3) utilizing the temperature sensor to sample the temperature, measuring the frequency output at the corresponding temperature, calculating the frequency offset acc according to a reference frequency, fitting the k value of a function of the temperature and the frequency offset based on the large amount of data so as to a temperature-frequency offset table, and looking for the table to obtain the accurate frequency offset PPM value through software; and (4) writing the corresponding value to the prescaler register and calibration register of the RTC during the service program interruption of the RTC.

Description

technical field [0001] The invention relates to a method for realizing accurate timing of clocks with built-in RTCs in various single-phase, three-phase and multi-function electric energy meters. Background technique [0002] At present, the traditional electric energy meter clock usually adopts an independent RTC mode with temperature compensation. Using this mode requires additional wiring, occupies MUC resources, and requires a large investment. The MUC built-in RTC has great advantages in performance and price, but because of the use of an external crystal, it is easily affected by temperature and generates frequency offset, resulting in the error of the MCU built-in RTC being much larger than that of an independent RTC with temperature compensation. As a result, the clock of the energy meter is inaccurate. Therefore, how to adjust the prescaler register and clock calibration register of the MCU built-in RTC according to the crystal oscillation characteristics and tempe...

AI Technical Summary

Problems solved by technology

[0002] At present, the traditional electric energy meter clock usually adopts an independent RTC mode with temperature compensation. Using this mode requires additional wiring, occupies MUC resources, and requires a large investment.

The MUC built-in RTC has great advantages in performance and price, but because of the use of an external crystal, it is easily affected by temperature and generates frequency offset, resulting in the error of the MCU built-in RTC being much larger than that of an independent RTC with temperature compensation. As a result, the clock of the energy meter is inaccurate

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