Document information | NXP Semiconductors PCF2123 instruction

UM10301

User Manual for NXP Real Time Clocks PCF85x3, PCA8565 and PCF2123, PCA2125

Rev. 01 — 23 December 2008

User manual

Document information

Info	Content

Keywords	PCF8563, PCF8573, PCF8583, PCF8593, PCA8565, PCF2123,
	PCA2125, PCF2120, RTC, real time clock, timekeeping, crystal,
	32.768 kHz, backup.

Abstract	This application note aims to assist a user of above mentioned Real Time
	Clocks in achieving succesful design-in and application. It contains useful
	hints with respect to electrical schematic and PCB layout as well as code
	examples for the well established NXP PCF8563 and related Real Time
	Clocks. Also the more recent Real Time Clocks PCF2123 and PCA2125
	have been taken into account.

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NXP Semiconductors PCF2123, PCF85x3, PCA8565, PCA2125 user manual Document information, Info Content Keywords, Abstract

Contents

Document information Info Content KeywordsAbstract NXP Semiconductors Contact informationRevision history Rev Date Description Introduction Features Address Register name Bit Register overview PCF8563 Comparison Event counter mode Comparison of six real time clocks Features Power-on reset Power-on reset PORVoltage-low detector Voltage-low detection OscillatorOscillator-stop detection Overview of internal and external oscillator capacitors Pierce Oscillator equivalent diagram Oscillator frequency determining components UM10301 + C Parameter Value Unit Source Typical values for crystal and surrounding capacitors Oscillation allowance Using an external oscillator Crystal and crystal selection Modes which don’t work Effect of temperature − f nom Capacitors and capacitor selection Accuracy Influences on time accuracy Oscillator tuning Oscillator tuning 10.1 PCF2123 Offset register Century tracking Century and leap year, Daylight Saving TimeYear and leap year tracking Daylight Saving Time DST Initialization of the RTC and setting the time Initialization and setting of alarm and timerBlock Diagram PCF8563 Setting the alarm AlarmBinary BCD Register Comments Address Alarm function Setting the timer Setting the timerRegister Lithium Primary cells Backup power supply Backup circuit using primary lithium cell NiCd and NiMH secondary batteries Backup circuit using secondary cell NiCd or NiMH 13.3 Capacitors Charging the backup capacitor Some suggestions for diode D1 Diode selection1N4148 BAS716 BAS116 BAV170 PCB layout guidelines PCB layout proposal for PCF8563 using leaded components Partial circuit switch down Protection diodes Hints to keep power consumption low 0007 Rpmax as a function of bus capacitance 8473 ⋅ C b Application diagram 2, SPI interface Application diagram 1, I2C-bus interface Timer delays First period inaccuracy when using the timerTimer Source clock frequency Delay for n = General countdown timer behaviour Timer source clock Minimum timer period Maximum timer period First period delay for timer counter value n Timing requirements for I2C read and write I2C interface Block diagram I2C interface and Time counters Sequence of events example Read Oscillator startup time Checking for oscillation Troubleshooting No communication via I2C-bus Wrong time and date, wrong clock speed References Definitions Legal informationDisclaimers Trademarks Contents