PCA2125 SPI Real-time clock/calendar Rev. 01 — 28 July 2008 Product data sheet 1. General description The PCA2125 is a CMOS real-time clock/calendar optimized for low-power consumption and an operating temperature up to 125 °C. Data is transferred via a Serial Peripheral Interface (SPI) bus with a maximum data rate of 6.0 Mbit/s. An alarm and timer function are also available with the possibility to generate a wake-up signal on an interrupt pin. AEC Q100 qualified for automotive applications. 2. Features n Provides year, month, day, weekday, hours, minutes and seconds based on 32.768 kHz quartz crystal n Resolution: seconds to years n Clock operating voltage: 1.3 V to 5.5 V n Low backup current: typical 0.55 µA at VDD = 3.0 V and Tamb = 25 °C n 3-line SPI-bus with separate combinable data input and output n Serial interface (at VDD = 1.6 V to 5.5 V) n 1 second or 1 minute interrupt output n Freely programmable timer with interrupt capability n Freely programmable alarm function with interrupt capability n Integrated oscillator capacitor n Internal power-on reset n Open-drain interrupt pin 3. Applications n Automotive time keeping application n Metering 4. Ordering information Table 1. Ordering information Type number PCA2125TS Package Name Description Version TSSOP14 plastic thin shrink small outline package; 14 leads; body width 4.4 mm SOT402-1 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 5. Marking Table 2. Marking codes Type number Marking code PCA2125TS PCA2125 6. Block diagram OSCI OSCILLATOR 32.768 kHz DIVIDER CLOCK OUT CLKOUT OSCO CONTROL MONITOR 00h Control_1 01h Control_2 0Dh CLKOUT_control POWER-ON RESET TIME 02h Seconds VDD 03h Minutes VSS 04h Hours WATCHDOG 05h Days 06h Weekdays 07h Months 08h Years ALARM FUNCTION SDO SDI SCL SPI INTERFACE 09h Minute_alarm 0Ah Hour_alarm 0Bh Day_alarm 0Ch Weekday_alarm INT INTERRUPT CE TIMER FUNCTION PCA2125 0Eh Timer_control 0Fh Countdown_timer 001aah664 Fig 1. Block diagram of PCA2125 PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 2 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 7. Pinning information 7.1 Pinning 14 VDD 13 CLKOUT OSCI 1 OSCO 2 n.c. 3 n.c. 4 INT 5 10 SCL CE 6 9 SDI VSS 7 8 SDO 12 n.c. PCA2125 11 n.c. 001aaf892 Fig 2. Pin configuration for TSSOP14 7.2 Pin description Table 3. Pin description Symbol Pin Description OSCI 1 oscillator input OSCO 2 oscillator output n.c. 3, 4 not connected; do not connect and do not use as feed through; connect to VDD if floating pins are not allowed INT 5 interrupt output (open-drain; active LOW) CE 6 chip enable input (active HIGH) with 200 kΩ pull-down resistor VSS 7 ground SDO 8 serial data output, push-pull SDI 9 serial data input; might float when CE inactive SCL 10 serial clock input; might float when CE inactive n.c. 11, 12 not connected; do not connect and do not use as feed through; connect to VDD if floating pins are not allowed CLKOUT 13 clock output (open-drain) VDD 14 supply voltage 8. Functional description The PCA2125 contains sixteen 8-bit registers with an auto-incrementing address register, an on-chip 32.768 kHz oscillator with one integrated capacitor, a frequency divider which provides the source clock for the Real-Time Clock (RTC), a programmable clock output, and a 6 MHz SPI-bus. All sixteen registers are designed as addressable 8-bit parallel registers although not all bits are implemented: PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 3 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar • The first two registers at addresses 00h and 01h (Control_1 and Control_2) are used as control registers. • Registers at addresses 02h to 08h (Seconds, Minutes, Hours, Days, Weekdays, Months, Years) are used as counters for the clock function. Seconds, minutes, hours, days, months and years are all coded in Binary Coded Decimal (BCD) format. When one of the RTC registers is read the contents of all counters are frozen. Therefore, faulty reading of the clock/calendar during a carry condition is prevented. • Registers at addresses 09h to 0Ch (Minute_alarm, Hour_alarm, Day_alarm, Weekday_alarm) define the alarm condition. • Register at address 0Dh (CLKOUT_control) defines the clock out mode. • Registers at addresses 0Eh and 0Fh (Timer_control and Countdown_timer) are used for the countdown timer function. The countdown timer has four selectable source clocks allowing for countdown periods in the range from less than 1 ms to more than 4 hours. There are also two pre-defined timers which can be used to generate an interrupt once per second or once per minute. These are defined in register Control_2 (01h). 8.1 Register overview The time registers are encoded in BCD to simplify application use. Other registers are either bit-wise or standard binary. Table 4. Register overview Bits labeled ‘-’ are not implemented and will return a logic 0 when read. Bit positions labeled ‘0’ should always be written with logic 0. Address Register name Bit 7 6 5 4 3 2 1 0 00h Control_1 EXT_TEST 0 STOP 0 POR_OVRD 12_24 0 0 01h Control_2 MI SI MSF TI_TP AF TF AIE TIE 02h Seconds RF SECONDS[1] SECONDS - MINUTES[1] MINUTES 03h Minutes 04h Hours - HOURS[2] HOURS DAYS[1] DAYS Days - - 06h Weekdays - - 07h Months 08h Years 09h Minute_alarm 0Ah Hour_alarm HOURS - 05h - - AMPM HOURS[1] - - - MONTHS[1] - MONTHS YEARS[1] AEN_H YEARS MINUTE_ALARM[1] AEN_M - AMPM WEEKDAYS MINUTE_ALARM HOUR_ALARM[1] HOUR_ALARM - HOUR_ALARM[2] 0Bh Day_alarm AEN_D - DAY_ALARM[1] 0Ch Weekday_alarm AEN_W - - - - WEEKDAY_ALARM 0Dh CLKOUT_control - - - - - COF 0Eh Timer_control TE - - - - 0Fh Countdown_timer [1] HOUR_ALARM DAY_ALARM - CTD COUNTDOWN_TIMER Ten’s place. PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 4 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar [2] Ten’s place in 24 h mode. 8.2 Reset The PCA2125 includes an internal reset circuit which is active whenever the oscillator is stopped; see Figure 3. The oscillator can be stopped, for example, by connecting one of the oscillator pins OSCI or OSCO to ground. OSCILLATOR SDI CE osc stopped 0 = stopped, 1 = running POR OVERRIDE 0 = override inactive 1 = override active CLEAR Bit POR_OVRD Fig 3. reset 0 = clear override mode 1 = override possible 001aaf898 Reset system The oscillator is considered to be stopped during the time between power-up and stable crystal resonance; see Figure 4. This time can be in the range 200 ms to 2 s depending on crystal type, temperature and supply voltage. Whenever an internal reset occurs, the reset flag bit RF is set. chip in reset chip not in reset VDD oscillation internal reset t 001aaf897 Fig 4. Power-on reset Table 5. Register reset value Bits labeled ‘-’ are not implemented and will return a ‘0’ when read. Bits labeled ‘X’ are undefined at power-up and unchanged by subsequent resets. Address Register name Bit 7 6 5 4 3 2 1 0 00h Control_1 0 0 0 - 1 0 - - 01h Control_2 0 0 0 0 0 0 0 0 02h Seconds 1 X X X X X X X 03h Minutes - X X X X X X X 04h Hours - - X X X X X X 05h Days - - X X X X X X 06h Weekdays - - - - - X X X PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 5 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar Table 5. Register reset value …continued Bits labeled ‘-’ are not implemented and will return a ‘0’ when read. Bits labeled ‘X’ are undefined at power-up and unchanged by subsequent resets. Address Register name Bit 7 6 5 4 3 2 1 0 07h Months - - - X X X X X 08h Years X X X X X X X X 09h Minute_alarm 1 X X X X X X X 0Ah Hour_alarm 1 - X X X X X X 0Bh Day_alarm 1 - X X X X X X 0Ch Weekday_alarm 1 - - - - X X X 0Dh CLKOUT_control - - - - - 0 0 0 0Eh Timer_control 0 - - - - - 1 1 0Fh Countdown_timer X X X X X X X X After reset, the following mode is entered: • 32.768 kHz on pin CLKOUT active • Power-on reset override available to be set • 24 hour mode is selected The SPI-bus is initialized whenever the chip enable pin CE is inactive (LOW). 8.2.1 Power-on reset override The Power-On Reset (POR) duration is directly related to the crystal oscillator start-up time. Due to the long start-up times experienced by these types of circuits, a mechanism has been built in to disable the POR and hence speed up the on-board test of the device. The setting of this mode requires that bit POR_OVRD be set to logic 1 and that the signals at the SPI-bus pins SDI and CE are toggled as illustrated in Figure 5. All timings are required minimums. Once the override mode has been entered, the device immediately stops being reset and set-up operation can commence i.e. entry into the external clock test mode via the SPI-bus access. The override mode can be cleared by writing a logic 0 to bit POR_OVRD. Bit POR_OVRD must be set to logic 1 before a re-entry into the override mode is possible. Setting bit POR_OVRD to logic 0 during normal operation has no effect except to prevent accidental entry into the POR override mode. This is the recommended setting. minimum 500 ns SDI CE reset override minimum 500 ns minimum 2000 ns POR override set at this time Fig 5. POR override sequence PCA2125_1 Product data sheet 001aaf900 © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 6 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 8.3 Control registers Table 6. Control_1 register (address 00h) bit description Bit Symbol Value Description Reference 7 EXT_TEST 0 normal mode Section 8.9 1 external clock test mode 6 - 0 unused 5 STOP 0 RTC source clock runs 1 RTC divider chain flip-flops are asynchronously set to logic 0; the RTC clock is stopped (CLKOUT at 32.768 kHz, 16.384 kHz or 8.192 kHz is still available) 0 unused - power-on reset override facility is disabled; set to logic 0 for normal operation Section 8.2.1 4 - 3 POR_OVRD 0 2 1 to 0 12_24 - Table 7. 1 power-on reset override is enabled 0 24 hour mode is selected 1 12 hour mode is selected 0 unused Table 11 - Control_2 register (address 01h) bit description Bit Symbol Value Description Reference 7 MI 0 Section 8.6.1 1 minute interrupt is enabled 6 SI 0 second interrupt is disabled 1 second interrupt is enabled 0 no minute or second interrupt generated 1 flag set when minute or second interrupt generated; flag must be cleared to clear interrupt 0 interrupt pin follows timer flags 1 interrupt pin generates a pulse 0 no alarm interrupt generated 1 flag set when alarm triggered; flag must be cleared to clear interrupt 0 no countdown timer interrupt generated 1 flag set when countdown timer interrupt generated; flag must be cleared to clear interrupt 0 no interrupt generated from the alarm flag 1 interrupt generated when alarm flag set 0 no interrupt generated from the countdown timer flag 1 interrupt generated when countdown timer flag set 5 4 3 2 1 0 MSF TI_TP AF TF AIE TIE minute interrupt is disabled PCA2125_1 Product data sheet Section 8.10 Section 8.6 Section 8.7.2 Section 8.5.1 - Section 8.7.3 Section 8.7 © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 7 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 8.4 Time and date function The majority of the registers are coded in the Binary Coded Decimal (BCD) format. BCD is used to simplify application use. An example is shown for register Minutes in Table 8. Table 8. BCD example Minutes value (decimal) Double-digit Digit Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 23 22 21 20 23 22 21 20 00 0 0 0 0 0 0 0 0 01 0 0 0 0 0 0 0 1 02 0 0 0 0 0 0 1 0 : : : : : : : : : 09 0 0 0 0 1 0 0 1 10 0 0 0 1 0 0 0 0 : : : : : : : : : 58 0 1 0 1 1 0 0 0 59 0 1 0 1 1 0 0 1 Table 9. Register Seconds (address 02h) bit description Bit Symbol Value Description 7 RF 0 clock integrity is guaranteed 1 clock integrity is not guaranteed; chip reset has occurred since flag was last cleared 00 to 59 this register holds the current seconds value coded in BCD format 6 to 0 SECONDS[6:0] Table 10. Register Minutes (address 03h) bit description Bit Symbol Value Description 7 - 0 unused 6 to 0 MINUTES[6:0] 00 to 59 this register holds the current minutes value coded in BCD format Table 11. Register Hours (address 04h) bit description Bit Symbol Value Description 6 and 7 - 0 unused 0 indicates AM 1 indicates PM 01 to 12 this register holds the current hours value coded in BCD format for 12 hour mode 00 to 23 this register holds the current hours value coded in BCD format for 24 hour mode 12 hour 5 mode[1] AMPM 4 to 0 HOURS[4:0] 24 hour mode[1] 5 to 0 [1] HOURS[5:0] Hour mode is set by bit 12_24 in register Control_1. PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 8 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar Table 12. Register Days (address 05h) bit description Bit Symbol Value Description 6, 7 - 0 unused 5 to 0 DAYS[5:0] 01 to 31 this register holds the current day value coded in BCD format[1] [1] The RTC compensates for leap years by adding a 29th day to February if the year counter contains a value which is exactly divisible by 4, including the year 00. Table 13. Register Weekdays (address 06h) bit description Bit Symbol Value Description 3 to 7 - 0 unused 2 to 0 WEEKDAYS[2:0] 0 to 6 this register holds the current weekday value; see Table 14 Table 14. Weekday assignments Day[1] Double-digit Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Sunday X X X X X 0 0 0 Monday X X X X X 0 0 1 Tuesday X X X X X 0 1 0 Wednesday X X X X X 0 1 1 Thursday X X X X X 1 0 0 Friday X X X X X 1 0 1 Saturday X X X X X 1 1 0 [1] The weekday assignments can be re-defined by the user. Table 15. Register Months (address 07h) bit description Bit Symbol Value Description 5 to 7 - 0 unused 4 to 0 MONTHS[4:0] 01 to 12 this register holds the current month value coded in BCD format; see Table 16 Table 16. Month assignments Month Double-digit Digit Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 January X X X 0 0 0 0 1 February X X X 0 0 0 1 0 March X X X 0 0 0 1 1 April X X X 0 0 1 0 0 May X X X 0 0 1 0 1 June X X X 0 0 1 1 0 July X X X 0 0 1 1 1 August X X X 0 1 0 0 0 September X X X 0 1 0 0 1 PCA2125_1 Product data sheet Digit © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 9 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar Table 16. Month assignments …continued Month Double-digit Digit Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 October X X X 1 0 0 0 0 November X X X 1 0 0 0 1 December X X X 1 0 0 1 0 Table 17. Register Years (address 08h) bit description Bit Symbol Value Description 7 to 0 YEARS[7:0] 00 to 99 this register holds the current year value coded in BCD format Figure 6 shows the data flow and data dependencies starting from the 1 Hz clock tick. 1 Hz tick SECONDS MINUTES 12_24 hour mode HOURS LEAP YEAR CALCULATION DAYS WEEKDAY MONTHS YEARS Fig 6. 001aaf901 Data flow for the time function 8.5 Alarm function When one or several alarm registers are loaded with a valid minute, hour, day or weekday value and its corresponding alarm enable not bit (AENx) is logic 0, then that information is compared with the current minute, hour, day and weekday value. Table 18. Register Minute_alarm (address 09h) bit description Bit Symbol Value Description 7 AEN_M 0 minute alarm is enabled 1 minute alarm is disabled 00 to 59 this register holds the minute alarm value coded in BCD format 6 to 0 MINUTE_ALARM[6:0] PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 10 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar Table 19. Register Hour_alarm (address 0Ah) bit description Bit Symbol Value Description 7 AEN_H 0 hour alarm is enabled 1 hour alarm is disabled 6 - 0 unused 0 indicates AM 1 indicates PM 01 to 12 this register holds the hour alarm value coded in BCD format when in 12 hour mode 00 to 23 this register holds the hour alarm value coded in BCD format when in 24 hour mode 12 hour mode 5 AMPM 4 to 0 HOUR_ALARM 24 hour mode 5 to 0 HOUR_ALARM Table 20. Register Day_alarm (address 0Bh) bit description Bit Symbol Value Description 7 AEN_D 0 day alarm is enabled 1 day alarm is disabled 6 - 0 unused 5 to 0 DAY_ALARM 01 to 31 this register holds the day alarm value coded in BCD format Table 21. Register Weekday_alarm (address 0Ch) bit description Bit Symbol Value Description 7 AEN_W 0 weekday alarm is enabled 1 weekday alarm is disabled 3 to 6 - 0 unused 2 to 0 WEEKDAY_ALARM 0 to 6 this register holds the weekday alarm value PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 11 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar check now signal example MINUTE AEN MINUTE AEN = 1 MINUTE ALARM = 1 0 MINUTE TIME HOUR AEN HOUR ALARM = HOUR TIME set alarm flag, AF DAY AEN DAY ALARM = DAY TIME WEEKDAY AEN WEEKDAY ALARM = 001aaf902 WEEKDAY TIME Fig 7. Alarm function block diagram Generation of interrupts from the alarm function is described in Section 8.7.3. 8.5.1 Alarm flag When all enabled comparisons first match, the alarm flag bit AF is set. Bit AF will remain set until cleared by software. Once bit AF has been cleared it will only be set again when the time increments once more to match the alarm condition. Alarm registers which have their bit AENx at logic 1 are ignored. Figure 8 shows an example for clearing bit AF, but leaving bit MSF and bit TF unaffected. The flags are cleared by a write command, therefore bits 7, 6, 4, 1 and 0 must be written with their previous values. Repeatedly re-writing these bits has no influence on the functional behavior. minutes counter 44 minute alarm 45 45 46 AF INT when AIE = 1 001aaf903 Example where only the minute alarm is used and no other interrupts are enabled. Fig 8. Alarm flag timing PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 12 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar To prevent the timer flags being overwritten while clearing bit AF, a logic AND is performed during a write access. The flag is reset by writing a logic 0 but its value is not affected by writing a logic 1. Table 22. Flag location in register Control_2 Register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Control_2 - - MSF - AF TF - - Table 23 shows what instruction must be sent to clear bit AF. In this example, bit MSF and bit TF are unaffected. Table 23. Example to clear only AF (bit 3) in register Control_2 Register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Control_2 - - 1 - 0 1 - - 8.6 Timer functions The countdown timer has four selectable source clocks allowing for countdown periods in the range from less than 1 ms to more than 4 hours. There are also two pre-defined timers which can be used to generate an interrupt once per second or once per minute. Registers Control_2 (01h), Timer_control (0Eh) and Countdown_timer (0Fh) are used to control the timer function and output. Table 24. Table 25. Register Timer_control (address 0Eh) bit description Bit Symbol Value Description Reference 7 TE 0 countdown timer is disabled Section 8.6.2 1 countdown timer is enabled 6 to 2 - 0 unused 1 to 0 CTD[1:0] 00 4096 Hz countdown timer source clock 01 64 Hz countdown timer source clock 10 1 Hz countdown timer source clock 11 1⁄ Hz 60 countdown timer source clock Register Countdown_timer (address 0Fh) bit description Bit Symbol Value Description Reference 7 to 0 COUNTDOWN_TIMER[7:0] 00h to FFh countdown value = n. Section 8.6.2 n CountdownPeriod = --------------------------------------------------------------SourceClockFrequency 8.6.1 Second and minute interrupt The second and minute interrupts (bits SI and MI) are pre-defined timers for generating periodic interrupts. The timers can be enabled independently of one another, however a minute interrupt enabled on top of a second interrupt will not be distinguishable since it will occur at the same time; see Figure 9. PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 13 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar seconds counter 58 59 minutes counter 59 00 11 12 00 01 INT MSF 001aai520 a. INT and MSF when SI enabled (MSF flag not cleared after an interrupt) seconds counter 58 59 minutes counter 59 00 11 12 00 01 INT MSF 001aai521 b. INT and MSF when only MI enabled Bit TI_TP is set to logic 1 resulting in 1⁄64 Hz wide interrupt pulse. Fig 9. Table 26. INT example for bits SI and MI Effect of bits MI and SI on INT generation Minute interrupt (bit MI) Second interrupt (bit SI) Result 0 0 no interrupt generated 1 0 an interrupt once per minute 0 1 an interrupt once per second 1 1 an interrupt once per second The minute and second flag (bit MSF) is set to logic 1 when either the seconds or the minutes counter increments according to the currently enabled interrupt. The flag can be read and cleared by the interface. The status of bit MSF does not affect the INT pulse generation. If the MSF flag is not cleared prior to the next coming interrupt period, an INT pulse will still be generated. The purpose of the flag is to allow the controlling system to interrogate the PCA2125 and identify the source of the interrupt such as the minute/second or countdown timer. PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 14 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar Table 27. Effect of bits MI and SI on bit MSF Minute interrupt (bit MI) Second interrupt (bit SI) Result 0 0 MSF never set 1 0 MSF set when minutes counter increments[1] 0 1 MSF set when seconds counter increments 1 1 MSF set when seconds counter increments [1] In the case of bit MI = 1 and bit SI = 0, bit MSF will be cleared automatically after 1 second. 8.6.2 Countdown timer function The 8-bit countdown timer at address 0Fh is controlled by the timer control register at address 0Eh. The timer control register determines one of 4 source clock frequencies for the timer (4096 Hz, 64 Hz, 1 Hz, or 1⁄60 Hz), and enables or disables the timer. Table 28. Bits CTD1 and CTD0 for timer frequency selection and countdown timer durations Bits CTD[1:0] Timer source clock frequency Delay 00 4096 Hz 244 µs 62.256 ms 01 64 Hz 15.625 ms 3.984 s 10 1 Hz 1s 255 s 11 1⁄ 60 [1] Hz Minimum timer duration Maximum timer duration n=1 n = 255 60 When not in use, bits CTD[1:0] must be set to s[1] 1⁄ 60 4 h 15 min Hz for power saving. Remark: Note that all timings which are generated from the 32.768 kHz oscillator are based on the assumption that there is 0 ppm deviation. Deviation in oscillator frequency will result in a corresponding deviation in timings. This is not applicable to interface timing. The timer counts down from a software-loaded 8-bit binary value n. Loading the counter with 0 effectively stops the timer. Values from 1 to 255 are valid. When the counter reaches 1, the countdown timer flag (bit TF) will be set and the counter automatically re-loads and starts the next timer period. Reading the timer will return the current value of the countdown counter; see Figure 10. PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 15 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar countdown value, n xx 03 xx 03 timer source clock countdown counter 02 01 03 02 01 03 02 01 03 TE TF INT n n duration of first timer period after enable may range from n − 1 to n + 1 001aaf906 In the example it is assumed that the timer flag is cleared before the next countdown period expires and that the INT is set to pulsed mode. Fig 10. General countdown timer behavior If a new value of n is written before the end of the current timer period, then this value will take immediate effect. NXP Semiconductors does not recommend changing n without first disabling the counter (by setting bit TE = 0). The update of n is asynchronous with the timer clock, therefore changing it without setting bit TE = 0 will result in a corrupted value loaded into the countdown counter which results in an undetermined countdown period for the first period. The countdown value n will however be correctly stored and correctly loaded on subsequent timer periods. When the countdown timer flag is set, an interrupt signal on INT will be generated provided that this mode is enabled. See Section 8.7.2 for details on how the interrupt can be controlled. When starting the timer for the first time, the first period will have an uncertainty which is a result of the enable instruction being generated from the interface clock which is asynchronous with the timer source clock. Subsequent timer periods will have no such delay. The amount of delay for the first timer period will depend on the chosen source clock; see Table 29. Table 29. First period delay for timer counter value n Timer source clock Minimum timer period Maximum timer period 4096 Hz n n+1 64 Hz n n+1 1 Hz (n − 1) + Hz n + 1⁄64 Hz 1⁄ 60 (n − 1) + 1⁄64 Hz n + 1⁄64 Hz Hz 1⁄ 64 At the end of every countdown, the timer sets the countdown timer flag (bit TF). Bit TF can only be cleared by software. The asserted bit TF can be used to generate an interrupt (INT). The interrupt can be generated as a pulsed signal every countdown period or as a permanently active signal which follows the condition of bit TF. Bit TI_TP is used to control this mode selection and the interrupt output can be disabled with bit TIE. PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 16 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar When reading the timer, the current countdown value is returned and not the initial value n. For accurate read back of the countdown value, the SPI-bus clock (SCL) must be operating at a frequency of at least twice the selected timer clock. Since it is not possible to freeze the countdown timer counter during read back, it is recommended to read the register twice and check for consistent results. 8.6.3 Timer flags When a minute or second interrupt occurs, bit MSF is set to logic 1. Similarly, at the end of a timer countdown, bit TF is set to logic 1. These bits maintain their value until overwritten by software. If both countdown timer and minute/second interrupts are required in the application, the source of the interrupt can be determined by reading these bits. To prevent one flag being overwritten while clearing another, a logic AND is performed during a write access. The flag is reset by writing a logic 0 but its value is not affected by writing a logic 1. Three examples are given for clearing the flags. Flags MSF and TF are cleared by a write command, therefore bits 7, 6, 4, 1 and 0 must be written with their previous values. Repeatedly re-writing these bits has no influence on the functional behavior. Table 30. Flag location in register Control_2 Register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Control_2 - - MSF - AF TF - - Table 31, Table 32 and Table 33 show what instruction must be sent to clear the appropriate flag. Table 31. Example to clear only TF (bit 2) in register Control_2 Register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Control_2 - - 1 - 1 0 - - Table 32. Example to clear only MSF (bit 5) in register Control_2 Register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Control_2 - - 0 - 1 1 - - Table 33. Example to clear both TF and MSF (bits 2 and 5) in register Control_2 Register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Control_2 - - 0 - 1 0 - - Clearing the alarm flag (bit AF) operates in exactly the same way; see Section 8.5.1. 8.7 Interrupt output An active LOW interrupt signal is available at pin INT. Operation is controlled via the bits of control register 2. Interrupts can be sourced from three places: second/minute timer, countdown timer and alarm function. Bit TI_TP configures the timer generated interrupts to be either a pulse or to follow the status of the interrupt flags (bits TF and MSF). PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 17 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar SI MSF: MINUTE SECOND FLAG SET SECONDS COUNTER MINUTES COUNTER CLEAR MI to interface: read MSF SI MI 0 PULSE GENERATOR 1 TRIGGER 1 CLEAR from interface: clear MSF TE TF: TIMER COUNTDOWN COUNTER INT TI_TP to interface: read TF TIE 0 SET CLEAR PULSE GENERATOR 2 TRIGGER 1 CLEAR from interface: clear TF set alarm flag, AF AF: ALARM FLAG SET to interface: read AF CLEAR AIE 001aaf907 from interface: clear AF When bits SI, MI, TIE and AIE are all disabled, pin INT will remain high-impedance. Fig 11. Interrupt scheme Remark: Note that the interrupts from the three groups are wired-OR, meaning they will mask one another; see Figure 11. 8.7.1 Minute and second interrupts The pulse generator for the minute/second interrupt operates from an internal 64 Hz clock and consequently generates a pulse of 1⁄64 second duration. If the MSF flag is clear before the end of the INT pulse, then the INT pulse is shortened. This allows the source of a system interrupt to be cleared immediately it is serviced i.e. the system does not have to wait for the completion of the pulse before continuing; see Figure 12. Instructions for clearing MSF are given in Section 8.6.3. PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 18 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar seconds counter 58 59 MSF INT (1) SCL 8th clock CLEAR INSTRUCTION instruction 001aaf908 (1) Indicates normal duration of INT pulse (bit TI_TP = 1). Fig 12. Example of shortening the INT pulse by clearing the MSF flag The timing shown for clearing bit MSF in Figure 12 is also valid for the non-pulsed interrupt mode i.e. when bit TI_TP = 0, where the pulse can be shortened by setting both bits MI and SI to logic 0. 8.7.2 Countdown timer interrupts Generation of interrupts from the countdown timer is controlled via bit TIE; see Table 7. The pulse generator for the countdown timer interrupt also uses an internal clock which is dependent on the selected source clock for the countdown timer and on the countdown value n. As a consequence, the width of the interrupt pulse varies; see Table 34. Table 34. INT operation (bit TI_TP = 1) Source clock (Hz) INT period (s) n = 1[1] n>1 4096 1⁄ 8192 1⁄ 4096 64 1⁄ 128 1⁄ 64 1 1⁄ 64 1⁄ 64 1⁄ 60 1⁄ 64 1⁄ 64 [1] n = loaded countdown value. Timer stopped when n = 0. If the TF flag is clear before the end of the INT pulse, then the INT pulse is shortened. This allows the source of a system interrupt to be cleared immediately it is serviced i.e. the system does not have to wait for the completion of the pulse before continuing; see Figure 13. Instructions for clearing TF are given in Section 8.6.3. PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 19 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar countdown counter 01 n TF INT (1) SCL 8th clock CLEAR INSTRUCTION instruction 001aaf909 (1) Indicates normal duration of INT pulse (bit TI_TP = 1). Fig 13. Example of shortening the INT pulse by clearing the TF flag The timing shown for clearing bit TF in Figure 13 is also valid for the non-pulsed interrupt mode i.e. when bit TI_TP = 0, where the pulse can be shortened by setting bit TIE = 0. 8.7.3 Alarm interrupts Generation of interrupts from the alarm function is controlled via bit AIE. If bit AIE is enabled, the INT pin follows the status of bit AF. Clearing bit AF will immediately clear INT. No pulse generation is possible for alarm interrupts; see Figure 14. minute counter 44 minute alarm 45 45 AF INT SCL 8th clock instruction CLEAR INSTRUCTION 001aaf910 Example where only the minute alarm is used and no other interrupts are enabled. Fig 14. AF timing PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 20 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 8.8 Clock output A programmable square wave is available at pin CLKOUT. Operation is controlled by control bits COF[2:0] in register CLKOUT_control (0Dh). Frequencies of 32.768 kHz (default) down to 1 Hz can be generated for use as a system clock, microcontroller clock, input to a charge pump, or for calibration of the oscillator. Pin CLKOUT is an open-drain output and enabled at power-on. When disabled the output is LOW. The duty cycle of the selected clock is not controlled, but due to the nature of the clock generation, all clock frequencies, except 32.768 kHz, have a duty cycle of 50 : 50. The ‘stop’ function can also affect the CLKOUT signal, depending on the selected frequency. When ‘stop’ is active, the CLKOUT pin will generate a continuous LOW for those frequencies that can be stopped. For more details, see Section 8.10. Table 35. CLKOUT frequency selection Bits COF[2:0] CLKOUT frequency (Hz) Typical duty cycle[1] (%) 000 32768 60 : 40 to 40 : 60 no effect 001 16384 50 : 50 no effect 010 8192 50 : 50 no effect 011 4096 50 : 50 CLKOUT = LOW 100 2048 50 : 50 CLKOUT = LOW 101 1024 50 : 50 CLKOUT = LOW 110 1 50 : 50 CLKOUT = LOW 111 CLKOUT = LOW [1] Effect of ‘stop’ Duty cycle definition: HIGH-level time (%) : LOW-level time (%). 8.9 External clock test mode A test mode is available which allows for on-board testing. In this mode it is possible to set up test conditions and control the operation of the RTC. The test mode is entered by setting bit EXT_TEST in register Control_1 making pin CLKOUT an input. The test mode replaces the internal signal with the signal applied to pin CLKOUT. Every 64 positive edges applied to pin CLKOUT generates an increment of one second. The signal applied to pin CLKOUT should have a minimum HIGH width of 300 ns and a minimum period of 1000 ns. The internal clock, now sourced from pin CLKOUT, is divided down to 1 Hz by a 26 divide chain called a prescaler; see Section 8.10. The prescaler can be set into a known state by using bit STOP. When bit STOP is set, the prescaler is reset to 0. STOP must be cleared before the prescaler can operate again. From a stop condition, the first 1 second increment will take place after 32 positive edges on pin CLKOUT. Thereafter, every 64 positive edges will cause a 1 second increment. Remark: Entry into test mode is not synchronized to the internal 64 Hz clock. When entering the test mode, no assumption as to the state of the prescaler can be made. Operation example: PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 21 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 1. Set EXT_TEST test mode (register Control_1, bit EXT_TEST = 1). 2. Set STOP (register Control_1, bit STOP = 1). 3. Clear STOP (register Control_1, bit STOP = 0). 4. Set time registers to desired value. 5. Apply 32 clock pulses to pin CLKOUT. 6. Read time registers to see the first change. 7. Apply 64 clock pulses to pin CLKOUT. 8. Read time registers to see the second change. Repeat steps 7 and 8 for additional increments. 8.10 STOP bit function The STOP bit function allows the accurate starting of the time circuits. The stop function will cause the upper part of the prescaler (F2 to F14) to be held at reset, thus no 1 Hz ticks will be generated. The time circuits can then be set and will not increment until the stop is released; see Figure 15. Stop will not affect the output of 32768 Hz, 16384 Hz or 8192 Hz; see Section 8.8. F2 RES F13 RES 2 Hz F1 reset 4096 Hz F0 8192 Hz OSC 16384 Hz 32768 Hz OSC STOP DETECTOR F14 1 Hz tick RES stop 512 Hz CLKOUT source 8192 Hz 16384 Hz 001aaf911 Fig 15. Stop bit functional diagram The lower two stages of the prescaler (F0 and F1) are not reset and because the SPI-bus is asynchronous to the crystal oscillator, the accuracy of re-starting the time circuits will be between 0 and one 8192 Hz cycle; see Figure 16. 8192 Hz stop released 0 µs to 122 µs 001aaf912 Fig 16. STOP bit release timing PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 22 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar The first increment of the time circuits is between 0.499888 s and 0.500000 s after stop is released. The uncertainty is caused by prescaler bits F0 and F1 not being reset; see Table 36. Table 36. Example: first increment of time circuits after stop release Bit STOP Prescaler bits F0F1-F2 to F14 [1] 1 Hz tick Time Comment hh:mm:ss Clock is running normally 0 01-0 0001 1101 0100 12:45:12 prescaler counting normally Stop is activated by user. F0F1 are not reset and values can not be predicted externally 1 XX-0 0000 0000 0000 12:45:12 prescaler is reset; time circuits are frozen 08:00:00 prescaler is reset; time circuits are frozen XX-0 0000 0000 0000 08:00:00 prescaler is now running XX-1 0000 0000 0000 08:00:00 XX-0 1000 0000 0000 08:00:00 XX-1 1000 0000 0000 08:00:00 : : 11-1 1111 1111 1110 08:00:00 00-0 0000 0000 0001 08:00:01 10-0 0000 0000 0001 08:00:01 : : 11-1 1111 1111 1111 08:00:01 00-0 0000 0000 0000 08:00:01 10-0 0000 0000 0000 08:00:01 : : 11-1 1111 1111 1110 08:00:01 00-0 0000 0000 0001 08:00:02 New time is set by user 1 XX-0 0000 0000 0000 Stop is released by user 0 [1] 0 to 1 transition of F14 increments the time circuits 0 to 1 transition of F14 increments the time circuits F0 is clocked at 32.768 kHz. 0.499888 s to 0.500000 s 1s 001aaf913 Fig 17. Increment of time circuit PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 23 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 8.11 3-line SPI Data transfer to and from the device is made via a 3-wire SPI-bus; see Table 37. The data lines for input and output are split. The data input and output lines can be connected together to facilitate a bidirectional data bus. The chip enable signal is used to identify the transmitted data. Each data transfer is a byte, with the Most Significant Bit (MSB) sent first; see Figure 18. Table 37. Serial interface Pin Function Description CE chip enable input when LOW, the interface is reset; pull-down resistor included; active input can be higher than VDD, but must not be wired HIGH permanently SCL serial clock input when pin CE = LOW, this input might float; input can be higher than VDD SDI serial data input when pin CE = LOW, this input might float; input can be higher than VDD; input data is sampled on the rising edge of SCL SDO serial data output push-pull output; drives from VSS to VDD; output data is changed on the falling edge of SCL The transmission is controlled by the active HIGH chip enable signal CE. The first byte transmitted is the command byte. Subsequent bytes will be either data to be written or data to be read. Data is captured on the rising edge of the clock and transferred internally on the falling edge. data bus COMMAND DATA DATA DATA chip enable 001aaf914 Fig 18. Data transfer overview The command byte defines the address of the first register to be accessed and the read/write mode. The address counter will auto increment after every access and will reset to zero after the last valid register is accessed. The read/write bit (R/W) defines if the following bytes will be read or write information. Table 38. Command byte definition Bit Symbol 7 R/W Value Description data read or data write selection 0 write data 1 read data subaddress; other codes will cause the device to ignore data transfer 6 to 4 SA 001 3 to 0 RA 00h to 0Fh register address range In Figure 19 the Seconds register is set to 45 seconds and the Minutes register to 10 minutes. PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 24 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar R/W b7 0 addr 02HEX b6 0 b5 0 b4 1 b3 0 b2 0 b1 1 seconds data 45BCD b0 0 b7 0 b6 1 b5 0 b4 0 b3 0 b2 1 minutes data 10BCD b1 0 b0 1 b7 0 b6 0 b5 0 b4 1 b3 0 b2 0 b1 0 b0 0 SCL SDI CE address counter xx 02 03 04 001aaf915 Fig 19. Serial bus write example In Figure 20 the Months and Years registers are read. In this example, pins SDI and SDO are not connected together. In this configuration, it is important that pin SDI is never left floating: it must always be driven either HIGH or LOW. If pin SDI is left open, high IDD currents will result. R/W b7 1 addr 07HEX b6 0 b5 0 b4 1 b3 0 b2 1 b1 1 months data 11BCD b0 1 b7 0 b6 0 b5 0 b4 1 b3 0 b2 0 years data 06BCD b1 0 b0 1 b7 0 b6 0 b5 0 b4 0 b3 0 b2 1 b1 1 b0 0 SCL SDI SDO CE address counter xx 07 08 09 001aaf916 Fig 20. Serial bus read example PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 25 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 9. Internal circuitry VDD OSCI CLKOUT OSCO SCL INT SDI CE SDO VSS PCA2125 001aaf895 Fig 21. Device diode protection diagram 10. Limiting values Table 39. Limiting values In accordance with the Absolute Maximum Rating System (IEC 60134). Symbol Parameter Min Max Unit VDD supply voltage −0.5 +6.5 V IDD supply current −50 +50 mA VI input voltage −0.5 +6.5 V VO output voltage −0.5 +6.5 V II input current −10 +10 mA IO output current −10 +10 mA Ptot total power dissipation - 300 mW Tamb ambient temperature −40 +125 °C Tstg storage temperature −65 +150 °C HBM [1] - ±2000 V MM [2] - ±200 V CDM [3] - ±2000 V [4] - 100 mA Vesd Ilu Conditions electrostatic discharge voltage latch-up current [1] HBM: Human Body Model, according to JESD22-A114. [2] MM: Machine Model, according to JESD22-A115. [3] CDM: Charged-Device Model, according to JESD22-C101. [4] Latch-up testing, according to JESD78. PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 26 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 11. Static characteristics Table 40. Static characteristics VDD = 1.3 V to 5.5 V; VSS = 0 V; Tamb = −40 °C to +125 °C; fosc = 32.768 kHz; quartz Rs = 60 kΩ; CL = 12.5 pF; unless otherwise specified. Symbol Parameter Conditions Min Typ Max Unit 1.3 - 5.5 V 1.6 - 5.5 V - - 500 µA - - 85 µA Tamb = 25 °C - 550 - nA Tamb = −40 °C to +125 °C - 760 1800 nA VDD = 5.0 V - 1000 - nA VDD = 3.0 V - 760 - nA VDD = 2.0 V - 640 - nA VDD = 5.0 V - - 2250 nA VDD = 3.0 V - - 1950 nA VDD = 2.0 V - - 1900 nA −0.5 - VDD + 0.5 V Supply: pin VDD VDD supply voltage SPI-bus inactive; for clock data integrity [1] SPI-bus active IDD supply current SPI-bus active fSCL = 6.0 MHz fSCL = 1.0 MHz SPI-bus inactive; CLKOUT disabled; VDD = 2.0 V to 5.0 V [2] SPI-bus inactive (fSCL = 0 Hz); CLKOUT enabled at 32 kHz Tamb = 25 °C Tamb = −40 °C to +125 °C Inputs VI input voltage pin OSCI pins CE, SDI, SCL VI input voltage −0.5 - 5.5 V VIL LOW-level input voltage VSS - 0.3VDD V VIH HIGH-level input voltage 0.7VDD - VDD V IL leakage current −1 0 +1 µA CI input capacitance - - 7 pF Rpd pull-down resistance pin CE - 240 550 kΩ VI = VDD or VSS; on pins SDI, SCL and OSCI [3] Outputs VO output voltage pins OSCO and SDO - - VDD + 0.5 V VO output voltage pins CLKOUT and INT; refers to external pull-up voltage - - 5.5 V VOH HIGH-level output voltage pin SDO 0.8VDD - VDD V VOL LOW-level output voltage pin SDO VSS - 0.2VDD V VOL LOW-level output voltage pins CLKOUT and INT; VDD = 5 V; IOL = 1.5 mA VSS - 0.4 V PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 27 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar Table 40. Static characteristics …continued VDD = 1.3 V to 5.5 V; VSS = 0 V; Tamb = −40 °C to +125 °C; fosc = 32.768 kHz; quartz Rs = 60 kΩ; CL = 12.5 pF; unless otherwise specified. Symbol Parameter Conditions Min Typ Max Unit IOH HIGH-level output current pin SDO; VOH = 4.6 V; VDD = 5 V - - 1.5 mA IOL LOW-level output current pins INT, SDO and CLKOUT; VOL = 0.4 V; VDD = 5 V −1.5 - - mA IOL LOW-level output current pin OSCO; VOL = 0.4 V; VDD = 5 V −1 - - mA ILO output leakage current VO = VDD or VSS −1 0 +1 µA Cext external capacitance - 25 - pF [1] For reliable oscillator start at power-up: VDD = VDD(min) + 0.3 V. [2] Timer source clock = 1⁄60 Hz; voltage on pins CE, SDI and SCL at VDD or VSS. [3] Implicit by design. 12. Dynamic characteristics Table 41. Dynamic characteristics VDD = 1.6 V to 5.5 V; VSS = 0 V; Tamb = −40 °C to +125 °C. All timing values are valid within the operating supply voltage at ambient temperature and referenced to VIL and VIH with an input voltage swing of VSS to VDD. Symbol Parameter Conditions VDD = 1.6 V VDD = 2.7 V VDD = 4.5 V VDD = 5.5 V Unit Min Max Min Max Min Max Min - 1.5 - 4.76 - 5.00 - Max Pin SCL fclk(SCL) SCL clock frequency 6.25 MHz tSCL SCL time 660 - 210 - 200 - 160 - ns tclk(H) clock HIGH time 320 - 100 - 100 - 70 - ns tclk(L) clock LOW time 320 - 110 - 100 - 90 - ns tr rise time - 100 - 100 - 100 - 100 ns tf fall time - 100 - 100 - 100 - 100 ns Pin CE tsu(CE) CE set-up time 30 - 30 - 30 - 30 - ns th(CE) CE hold time 100 - 60 - 40 - 30 - ns trec(CE) CE recovery time 100 - 100 - 100 - 100 - ns tw(CE) CE pulse width - 0.99 - 0.99 - 0.99 - 0.99 s Pin SDI tsu set-up time 25 - 15 - 15 - 10 - ns th hold time 100 - 60 - 40 - 30 - ns - 320 - 110 - 100 - 90 ns - 50 - 30 - 30 - 25 ns 0 - 0 - 0 - 0 - ns Pin SDO td(R)SDO tdis(SDO) SDO read delay time bus load = 85 pF SDO disable time tt(SDI-SDO) transition time from SDI to SDO [1] [1] no load value to avoid bus conflict Bus will be held up by bus capacitance; use RC time constant with application values. PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 28 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar tw(CE) CE tsu(CE) trec(CE) tr th(CE) tf 80% SCL 20% tclk(L) tclk(H) WRITE tsu th SDI SDO R/W SA2 RA0 b6 b0 b7 b6 b0 Hi Z READ SDI b7 tt(SDI-SDO) tdis(SDO) td(R)SDO SDO Hi Z b7 b6 b0 001aag900 Fig 22. SPI interface timing PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 29 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 13. Application information 13.1 Application diagram 1F supercapacitor OSCI VDD CLKOUT CE SCL OSCO PCA2125 SDI SDO INT VSS 001aaf918 The 1 farad capacitor is used as a standby and back-up supply. With the RTC in its minimum power configuration i.e. timer off and CLKOUT off, the RTC can operate for several weeks. Fig 23. Application diagram 13.2 Quartz frequency adjustment 1. Method 1: fixed OSCI capacitor A fixed capacitor can be used whose value can be determined by evaluating the average capacitance necessary for the application layout; see Figure 23. The frequency is best measured via the 32.768 kHz signal at pin CLKOUT available after power-on. The frequency tolerance depends on the quartz crystal tolerance, the capacitor tolerance and the device-to-device tolerance (on average ±5 × 10−6). An average deviation of ±5 minutes per year can be easily achieved. 2. Method 2: OSCI trimmer Fast setting of a trimmer is possible using the 32.768 kHz signal at pin CLKOUT available after power-on. 3. Method 3: OSCO output Direct measurement of OSCO output (accounting for test probe capacitance). 14. Test information 14.1 Quality information This product has been qualified in accordance with the Automotive Electronics Council (AEC) standard Q100 - Stress test qualification for integrated circuits, and is suitable for use in automotive applications. PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 30 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 15. Package outline TSSOP14: plastic thin shrink small outline package; 14 leads; body width 4.4 mm SOT402-1 E D A X c y HE v M A Z 8 14 Q (A 3) A2 A A1 pin 1 index θ Lp L 1 7 e detail X w M bp 0 2.5 5 mm scale DIMENSIONS (mm are the original dimensions) UNIT A max. A1 A2 A3 bp c D (1) E (2) e HE L Lp Q v w y Z (1) θ mm 1.1 0.15 0.05 0.95 0.80 0.25 0.30 0.19 0.2 0.1 5.1 4.9 4.5 4.3 0.65 6.6 6.2 1 0.75 0.50 0.4 0.3 0.2 0.13 0.1 0.72 0.38 8 o 0 o Notes 1. Plastic or metal protrusions of 0.15 mm maximum per side are not included. 2. Plastic interlead protrusions of 0.25 mm maximum per side are not included. OUTLINE VERSION SOT402-1 REFERENCES IEC JEDEC JEITA EUROPEAN PROJECTION ISSUE DATE 99-12-27 03-02-18 MO-153 Fig 24. Package outline SOT402-1 (TSSOP14) PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 31 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 16. Handling information Inputs and outputs are protected against electrostatic discharge in normal handling. However, to be completely safe you must take normal precautions appropriate to handling MOS devices; see JESD625-A and/or IEC61340-5. 17. Soldering of SMD packages This text provides a very brief insight into a complex technology. A more in-depth account of soldering ICs can be found in Application Note AN10365 “Surface mount reflow soldering description”. 17.1 Introduction to soldering Soldering is one of the most common methods through which packages are attached to Printed Circuit Boards (PCBs), to form electrical circuits. The soldered joint provides both the mechanical and the electrical connection. There is no single soldering method that is ideal for all IC packages. Wave soldering is often preferred when through-hole and Surface Mount Devices (SMDs) are mixed on one printed wiring board; however, it is not suitable for fine pitch SMDs. Reflow soldering is ideal for the small pitches and high densities that come with increased miniaturization. 17.2 Wave and reflow soldering Wave soldering is a joining technology in which the joints are made by solder coming from a standing wave of liquid solder. The wave soldering process is suitable for the following: • Through-hole components • Leaded or leadless SMDs, which are glued to the surface of the printed circuit board Not all SMDs can be wave soldered. Packages with solder balls, and some leadless packages which have solder lands underneath the body, cannot be wave soldered. Also, leaded SMDs with leads having a pitch smaller than ~0.6 mm cannot be wave soldered, due to an increased probability of bridging. The reflow soldering process involves applying solder paste to a board, followed by component placement and exposure to a temperature profile. Leaded packages, packages with solder balls, and leadless packages are all reflow solderable. Key characteristics in both wave and reflow soldering are: • • • • • • Board specifications, including the board finish, solder masks and vias Package footprints, including solder thieves and orientation The moisture sensitivity level of the packages Package placement Inspection and repair Lead-free soldering versus SnPb soldering 17.3 Wave soldering Key characteristics in wave soldering are: PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 32 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar • Process issues, such as application of adhesive and flux, clinching of leads, board transport, the solder wave parameters, and the time during which components are exposed to the wave • Solder bath specifications, including temperature and impurities 17.4 Reflow soldering Key characteristics in reflow soldering are: • Lead-free versus SnPb soldering; note that a lead-free reflow process usually leads to higher minimum peak temperatures (see Figure 25) than a SnPb process, thus reducing the process window • Solder paste printing issues including smearing, release, and adjusting the process window for a mix of large and small components on one board • Reflow temperature profile; this profile includes preheat, reflow (in which the board is heated to the peak temperature) and cooling down. It is imperative that the peak temperature is high enough for the solder to make reliable solder joints (a solder paste characteristic). In addition, the peak temperature must be low enough that the packages and/or boards are not damaged. The peak temperature of the package depends on package thickness and volume and is classified in accordance with Table 42 and 43 Table 42. SnPb eutectic process (from J-STD-020C) Package thickness (mm) Package reflow temperature (°C) Volume (mm3) < 350 ≥ 350 < 2.5 235 220 ≥ 2.5 220 220 Table 43. Lead-free process (from J-STD-020C) Package thickness (mm) Package reflow temperature (°C) Volume (mm3) < 350 350 to 2000 > 2000 < 1.6 260 260 260 1.6 to 2.5 260 250 245 > 2.5 250 245 245 Moisture sensitivity precautions, as indicated on the packing, must be respected at all times. Studies have shown that small packages reach higher temperatures during reflow soldering, see Figure 25. PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 33 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar temperature maximum peak temperature = MSL limit, damage level minimum peak temperature = minimum soldering temperature peak temperature time 001aac844 MSL: Moisture Sensitivity Level Fig 25. Temperature profiles for large and small components For further information on temperature profiles, refer to Application Note AN10365 “Surface mount reflow soldering description”. 18. Revision history Table 44. Revision history Document ID Release date Data sheet status PCA2125_1 20080728 Product data sheet PCA2125_1 Product data sheet Change notice Supersedes - © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 34 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 19. Legal information 20. Data sheet status Document status[1][2] Product status[3] Definition Objective [short] data sheet Development This document contains data from the objective specification for product development. Preliminary [short] data sheet Qualification This document contains data from the preliminary specification. Product [short] data sheet Production This document contains the product specification. [1] Please consult the most recently issued document before initiating or completing a design. [2] The term ‘short data sheet’ is explained in section “Definitions”. [3] The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status information is available on the Internet at URL http://www.nxp.com. 20.1 Definitions Draft — The document is a draft version only. The content is still under internal review and subject to formal approval, which may result in modifications or additions. NXP Semiconductors does not give any representations or warranties as to the accuracy or completeness of information included herein and shall have no liability for the consequences of use of such information. Short data sheet — A short data sheet is an extract from a full data sheet with the same product type number(s) and title. A short data sheet is intended for quick reference only and should not be relied upon to contain detailed and full information. For detailed and full information see the relevant full data sheet, which is available on request via the local NXP Semiconductors sales office. In case of any inconsistency or conflict with the short data sheet, the full data sheet shall prevail. 20.2 Disclaimers General — Information in this document is believed to be accurate and reliable. However, NXP Semiconductors does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information. Right to make changes — NXP Semiconductors reserves the right to make changes to information published in this document, including without limitation specifications and product descriptions, at any time and without notice. This document supersedes and replaces all information supplied prior to the publication hereof. Suitability for use — NXP Semiconductors products are not designed, authorized or warranted to be suitable for use in medical, military, aircraft, space or life support equipment, nor in applications where failure or malfunction of an NXP Semiconductors product can reasonably be expected to result in personal injury, death or severe property or environmental damage. NXP Semiconductors accepts no liability for inclusion and/or use of NXP Semiconductors products in such equipment or applications and therefore such inclusion and/or use is at the customer’s own risk. Applications — Applications that are described herein for any of these products are for illustrative purposes only. NXP Semiconductors makes no representation or warranty that such applications will be suitable for the specified use without further testing or modification. Limiting values — Stress above one or more limiting values (as defined in the Absolute Maximum Ratings System of IEC 60134) may cause permanent damage to the device. Limiting values are stress ratings only and operation of the device at these or any other conditions above those given in the Characteristics sections of this document is not implied. Exposure to limiting values for extended periods may affect device reliability. Terms and conditions of sale — NXP Semiconductors products are sold subject to the general terms and conditions of commercial sale, as published at http://www.nxp.com/profile/terms, including those pertaining to warranty, intellectual property rights infringement and limitation of liability, unless explicitly otherwise agreed to in writing by NXP Semiconductors. In case of any inconsistency or conflict between information in this document and such terms and conditions, the latter will prevail. No offer to sell or license — Nothing in this document may be interpreted or construed as an offer to sell products that is open for acceptance or the grant, conveyance or implication of any license under any copyrights, patents or other industrial or intellectual property rights. 20.3 Trademarks Notice: All referenced brands, product names, service names and trademarks are the property of their respective owners. 21. Contact information For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: [email protected] PCA2125_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev. 01 — 28 July 2008 35 of 36 PCA2125 NXP Semiconductors SPI Real-time clock/calendar 22. Contents 1 2 3 4 5 6 7 7.1 7.2 8 8.1 8.2 8.2.1 8.3 8.4 8.5 8.5.1 8.6 8.6.1 8.6.2 8.6.3 8.7 8.7.1 8.7.2 8.7.3 8.8 8.9 8.10 8.11 9 10 11 12 13 13.1 13.2 14 14.1 15 16 17 17.1 17.2 17.3 17.4 General description . . . . . . . . . . . . . . . . . . . . . . 1 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Ordering information . . . . . . . . . . . . . . . . . . . . . 1 Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Pinning information . . . . . . . . . . . . . . . . . . . . . . 3 Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . 3 Functional description . . . . . . . . . . . . . . . . . . . 3 Register overview . . . . . . . . . . . . . . . . . . . . . . . 4 Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Power-on reset override . . . . . . . . . . . . . . . . . . 6 Control registers . . . . . . . . . . . . . . . . . . . . . . . . 7 Time and date function . . . . . . . . . . . . . . . . . . . 8 Alarm function. . . . . . . . . . . . . . . . . . . . . . . . . 10 Alarm flag . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Timer functions . . . . . . . . . . . . . . . . . . . . . . . . 13 Second and minute interrupt. . . . . . . . . . . . . . 13 Countdown timer function . . . . . . . . . . . . . . . . 15 Timer flags . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Interrupt output . . . . . . . . . . . . . . . . . . . . . . . . 17 Minute and second interrupts . . . . . . . . . . . . . 18 Countdown timer interrupts. . . . . . . . . . . . . . . 19 Alarm interrupts . . . . . . . . . . . . . . . . . . . . . . . 20 Clock output . . . . . . . . . . . . . . . . . . . . . . . . . . 21 External clock test mode. . . . . . . . . . . . . . . . . 21 STOP bit function . . . . . . . . . . . . . . . . . . . . . . 22 3-line SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Internal circuitry. . . . . . . . . . . . . . . . . . . . . . . . 26 Limiting values. . . . . . . . . . . . . . . . . . . . . . . . . 26 Static characteristics. . . . . . . . . . . . . . . . . . . . 27 Dynamic characteristics . . . . . . . . . . . . . . . . . 28 Application information. . . . . . . . . . . . . . . . . . 30 Application diagram . . . . . . . . . . . . . . . . . . . . 30 Quartz frequency adjustment . . . . . . . . . . . . . 30 Test information . . . . . . . . . . . . . . . . . . . . . . . . 30 Quality information . . . . . . . . . . . . . . . . . . . . . 30 Package outline . . . . . . . . . . . . . . . . . . . . . . . . 31 Handling information. . . . . . . . . . . . . . . . . . . . 32 Soldering of SMD packages . . . . . . . . . . . . . . 32 Introduction to soldering . . . . . . . . . . . . . . . . . 32 Wave and reflow soldering . . . . . . . . . . . . . . . 32 Wave soldering . . . . . . . . . . . . . . . . . . . . . . . . 32 Reflow soldering . . . . . . . . . . . . . . . . . . . . . . . 33 18 19 20 20.1 20.2 20.3 21 22 Revision history . . . . . . . . . . . . . . . . . . . . . . . Legal information . . . . . . . . . . . . . . . . . . . . . . Data sheet status . . . . . . . . . . . . . . . . . . . . . . Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . Disclaimers. . . . . . . . . . . . . . . . . . . . . . . . . . . Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . Contact information . . . . . . . . . . . . . . . . . . . . Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 35 35 35 35 35 35 36 Please be aware that important notices concerning this document and the product(s) described herein, have been included in section ‘Legal information’. © NXP B.V. 2008. All rights reserved. For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: [email protected] Date of release: 28 July 2008 Document identifier: PCA2125_1