PCF85063 User Manual: Objective
Contents
1. PCF85063 User Manual V1 Markus Hintermann June 2012 Product Line CWG PCF85063 User Manual Objective Key features Hardware set up Software set up RTC tuning General COMPANY CONFIDENTIAL 2 PCF85063 PL CWG M Hintermann June 18 2012 Key feature PCF85063TP Realtime clock with very small form factor counting seconds minutes weekdays weeks month and years Electronic tuning Interrupt every 30s or every minute Interface 400kHz I C bus Package HWSON8 package 2 6 x 2 6 x 0 5 mm CLKOUT CLKen SPI INT ZC BUS Vss COMPANY CONFIDENTIAL 3 PCF85063 PL CWG M Hintermann June 18 2012 Hardware set up The RTC circuit just requires one external part a tuning fork quartz as resonator The oscillation capacitors are integrated and therefore no need for external capacitors The quartz crystal must be placed close to the RTC circuit avoiding long lines which may pick up noise Avoid any tracks with high frequency signals fast edges close to the RTC quartz or quartz interconnect The interface is the standard Fast Mode I2C bus operating up to 400kHz Adjust pull up values to match the required interface soeed keeping them as high impedance as possible for power system saving Ensure that the specified minimum requirements of the hold times t pw amp thcy are fulfilled Supply voltage The RIC is specified from 1 8 to 5 5V The RTC excluding the2. 10100000 read mode Read register 4 seconds e g 56 Seconds clock integitiy ok gt OS 0 Minutes ee e g 46 Minutes Hours are aan e g 23 PM 03h Days vann anne e g 15 15 Weekdays nn e g 04 Thursday Month vass raes e g 12 December Vear gane sann e g 11 20 11 12C bus Stop condition NPE COMPANY CONFIDENTIAL 7 PCF85063 PL CWG M Hintermann June 18 2012 Frequency tuning The 32kHz quartzes are typically sold with a tolerance of either 20 10 ppm at room temperature 11 5ppm corresponds to 1s day The quartzes feature a characteristic load capacity of either 7pF or 12 5pf Oscillators utilizing 7 pF quartzes feature a slightly lower power consumption where the quartzes of 12 5 pF have largest production quantities The tacks between quartz and RTG represent also some parasitic capacities and must be kept short The PCF85063 has a tuning facility where above tolerances can be compensated Tuning procedure Measure the 32xxx Hz f signal at the CLKOUT pin The offset is calculated in ppm as Afippmj 10 f 32768 32768 Consult the offset table in the data sheet Take the correction value and write it into the register O2h The correction is done by means of inhibition or addition the oscillator runs at constant speed then every 2 hours mode 0 1 second is corrected to by making it shorter or longer it is not easily visible at the CLKOUT Corrections can also be
3. applied every 4 minutes by using en 001229901 mode 1 This mode will consume more power tt dt 3270 The 32 kHz quartzes are of the type tuning fork and feature 2 a parabolic frequency response over temperature When typical use is over a limited temperature range it is often helpful to tune the frequency to be slight higher at the turn over point This is then compensated when the temperature is at either side of this e g For operation between 4 C 45 C tune the clock 8ppm AT faster th Idbeth lue for 25 aster than would be the value for 40 30 20 10 0 10 0 30 B0 90 C NPE COMPANY CONFIDENTIAL 8 PCF85063 PL CWG M Hintermann June 18 2012
4. C it can be activated by setting the EXT TEST bit in the Control 1 word The RTC 85063 has a frequency tuning facility its operation is explained in the specific chapter The RTC can stay switched on all the time There is no need to restart or reset the clock NG COMPANY CONFIDENTIAL 5 PCF85063 PL CWG M Hintermann June 18 2012 Software set up Setting the clock I2C bus Slave address Register address Status word 0 I2C bus Slave address Register address Seconds Minutes Hours Days Weekdays Month Year I2C bus X to 3 45 pm December 15 2011 Thursday Start condition 1010 0001 0000 0000 0000 0011 write bit set address pointer to status word 0 set 12h mode and select option for 12 5pF quartz repeated start condition 1010 0001 0000 0100 0000 0000 0100 0101 0100 0011 0001 0101 0000 0100 0001 0002 0001 0001 write bit set printer to seconds register 0 Seconds clock integrity ok gt MSB OS 0 45 min PM 3 clock integrity ok gt OS 0 15thn Thursday 4th day of the week December 20 11 Stop condition COMPANY CONFIDENTIAL 6 PCF85063 PL CWG M Hintermann June 18 2012 Software set up Reading the clock 2 minutes later than the writing I2C bus Start condition Slave address 10100001 write bit set Register address 0000 00100 address pointer to seconds byte 4 2C bus repeated start condition Slave address
5. I2C bus interface is however operating down to a lower voltage It is recommended to have a decoupling capacitor on the VDD VSS rails close by Due to the low power consumption of below 1 uW no precautions for heat dissipations are required CLKOUT can be used to measure the frequency Quartz i CLKOUT Not connected nr 33k INT Not connected Wi COMPANY CONFIDENTIAL 4 PCF85063 PL CWG M Hintermann June 18 2012 Software set up The RTC PCF85063 is controlled via standard I2C bus interface Common I2C protocol applies The interface is the standard Fast Mode I2C bus operating up to 400kHz Theoretically there is no low speed limit however the access of the RTC should be performed within less than 1 second otherwise second increments could be lost During access the time registers of the RTC are frozen and after the read or write sequence is completed a seconds increment is executed if required The clock tracks the actual time from seconds to year It must be initially set to the correct time of the actual time zone The days per month and leap year are corrected automatically Leap years are assumed whenever the year is divisible by 4 The RTC can be programmed to generate an interrupt every 30 second or every 60 seconds Byte number 03 is a general purpose RAM byte to store temporary information System testing there is a fast mode facility to test the functionality of the RT
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