PCF8563 Alternatives, Characteristics, Functions and More
20 March 2024
Ⅵ. Application circuit of PCF8563
Ⅷ. How is PCF8563 used in embedded systems?
PCF8563 is an industrial-grade multi-function clock chip with built-in I2C bus interface function produced by PHILIPS, with extremely low power consumption. The chip integrates a variety of alarm functions, timer functions, clock output functions and interrupt output functions. It can complete various complex timing services and provide watchdog functions for the microcontroller. Due to its excellent performance and extremely high cost performance, PCF8563 has been widely used in products such as telephones, fax machines, water meters, gas meters, electricity meters, portable instruments, and battery-powered instruments.
Alternatives and equivalents:
• SI52138-A16AGMR
• Century flag
• Voltage-low detector
• Alarm and timer functions
• Internal power-on reset
• Open drain interrupt pin
• Integrated oscillator capacitor
• I2C-bus slave address: read A3H and write A2H
• Wide operating supply voltage range: 1.0 to 5.5 V
• 400 kHz two-wire I2C-bus interface (at VDD = 1.8 to 5.5 V)
• Low backup current; typical 0.25 µA at VDD = 3.0 V and Temp = 25°C
• Programmable clock output for peripheral devices (32.768 kHz, 1.024kHz, 32 Hz and 1 Hz)
• Provides year, month, day, weekday, hours, minutes and seconds based on 32.768 kHz quartz crystal
1. Timer function mode
The timer of PCF8563 is a countdown timer, which is effective when TE=1. The countdown value is determined by the binary number in the OFH register. When the countdown value reaches 00, the TF bit will be set to 1. If E=1 is set at the same time, when TF is set to 1, it will generate an interrupt signal on the /INT pin. The interrupt signal is active at low level, similar to the alarm interrupt.
The timer interrupt signal of PCF8563 has two modes, which are controlled by the T/TP bit. When TI/TP=0 is set, the interrupt signal is the same as the alarm interrupt signal, both in low level mode. At this time, the interrupt signal can be cleared by setting TF=0. When TI/TP=1, the interrupt signal is in pulse mode, and its pulse low-level width is about 15ms. In this mode, the impact of the TF bit is negligible. It can be seen that TIE is equivalent to the timed interrupt enable control bit in the microcontroller, and TF is equivalent to the timed interrupt application flag. It is worth noting that the timer function and alarm function can be effective at the same time.
For example, if we want PCF8563 to generate an alarm every second and generate a pulse on the /INT terminal to the microcontroller P87LPC764, we can read the clock in the interrupt service program for display. This is one of the ways to display the clock. After completing the above configuration, a pulse interrupt signal with a period of 1s can be generated at the /INT pin. To clear the pulse interrupt, there are three methods: one is to clear the contents of the TIETE register to 0; the other is to clear the contents of the OFH register to 0; the third is to clear the interrupt through other control logic.
2. Alarm function mode
PCF8563 has four alarm modes, namely hour alarm, daily alarm, monthly alarm and weekly alarm. When an alarm occurs, the AF bit will change to 1. To make the alarm function effective, we need to set the highest bit AE of the corresponding alarm register to 0. If AIE=1 is set at the same time, it will generate an active low-level interrupt signal on the /INT pin while AF is set to 1. The way to clear the interrupt signal is to clear the AF bit through software. It can be seen that AIE is equivalent to the interrupt enable control bit in the microcontroller, while AF is equivalent to the interrupt application flag.
PCF8563 has 16 8-bit registers. These registers include an auto-incrementing address register, a built-in 32.768KHz oscillator (with an integrated capacitor), a frequency divider (providing the source clock for the real-time clock RTC), a programmable clock output, a timer, an alarm, a brownout detector and a 400KHz I2C bus interface.
All 16 registers are designed as addressable 8-bit parallel registers, but not all bits have actual functions. Among them, the first two registers (memory addresses 00H and 01H) are used as control registers and status registers respectively; memory addresses 02H to 08H are used for clock counters; addresses 09H to 0CH are alarm registers, used to define alarm conditions; address 0DH control The output frequency of the CLKOUT pin; and the addresses 0EH and 0FH are used for the timer control register and timer register respectively. The encoding format of the seconds, minutes, hours, days, months, years, and minute alarm, hour alarm, and day alarm registers is BCD; while the day of the week and weekday alarm registers are not encoded in the BCD format. When the RTC register is read, the contents of all counters are latched to ensure that no misreading of the clock calendar chip occurs during transmission.
The PCF8563 application circuit mainly includes a clock circuit, a chip connection power supply circuit and an I2C bus connection circuit.
First, the clock circuit uses an external crystal oscillator as the main frequency source to ensure accurate time calculation and display. The frequency of the oscillator can be adjusted as needed, and by selecting the appropriate frequency, for example, by utilizing an inverter circuit, the display of different time units such as seconds, minutes, hours, days, months, and years can be realized.
Second, the chip is connected to power supply circuits including battery power and external power in two ways. The battery power allows the PCF8563 to continue to operate without external power to maintain accurate time and date. The external power supply is then used to power and charge the chip. There is also a voltage regulator circuit to ensure that the chip is able to operate properly in the face of voltage fluctuations.
Finally, the I2C bus connection circuit is used to connect the PCF8563 to the main control device. Since the PCF8563 adopts the I2C bus communication protocol, the main control device can realize data transmission with the PCF8563 through the I2C bus, thereby completing multiple functions such as obtaining the time and date, and setting the alarm clock. The I2C bus connection circuit is mainly composed of the SCL clock line and the SDA data line. The signal is filtered and stabilized by connecting appropriate resistors and capacitors to ensure the reliability and accuracy of data transmission.
In accordance with the absolute maximum ratings system (IEC 60134).
The application of PCF8563 in embedded system mainly involves hardware connection and software setting. First of all, in terms of hardware connection, we need to connect the PCF8563 module with the microcontroller development board correctly. Since the PCF8563 module is equipped with an I2C interface, we need to connect the SDA (data line) and SCL (clock line) pins of the module to the corresponding pins on the MCU development board. In addition, to ensure the stable operation of the module, we also need to make sure that the power and ground lines are connected correctly to provide a stable operating voltage.
Second, in terms of software setup, we first need to make sure that the applicable development environment has been installed on the MCU development board and that the I2C bus has been correctly configured. Depending on the development board and programming language used, we may also need to install the appropriate libraries or drivers. When writing the code, we can utilize appropriate functions or commands to read the time and date information from the PCF8563 real-time clock module and display it on the serial monitor or other output device of the embedded system.
Frequently Asked Questions
1. What is the I2C address of PCF8563?
The PCF8563 I2C write address is 0xa2, and the read address is 0xa3.
2. Is PCF8563 suitable for low-power applications?
Yes, PCF8563 is designed for low power consumption, making it suitable for battery-powered devices and other applications where power efficiency is important.
3. What are the main features of PCF8563?
PCF8563 features include real-time clock/calendar, alarm functions, automatic compensation for leap years and months with fewer than 31 days, and low power consumption.
4. What is PCF8563?
The PCF8563 is a CMOS Real-Time Clock (RTC) and calendar optimized for low power consumption. A programmable clock output, interrupt output, and voltage-low detector are also provided. All addresses and data are transferred serially via a two-line bidirectional I²C-bus.
