Epson RX-8801SA/JE Applications Manual

Real time clock module
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Application Manua
Real Time Clock Module


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  • Page 1 ETM26E-03 Application Manua Real Time Clock Module RX-8801SA/JE...
  • Page 2 • The information, applied circuit, program, usage etc., written in this material is just for reference. Epson Toyocom does not assume any liability for the occurrence of infringing any patent or copyright of a third party. This material does not authorize the licensing for any patent or intellectual copyrights.
  • Page 3: Table Of Contents

    8.6.6. I C bus protocol ...25 8.7. Backup and Recovery...26 8.8. Connection with Typical Microcontroller...27 8.9. When used as a clock source (32 kHz-TCXO) ...27 9. External Dimensions / Marking Layout ... 28 10. Application notes ... 30 Contents C bus communications ...23...
  • Page 4: Overview

    C bus interface-compliant real-time clock which includes a 32.768 kHz DTCXO. In addition to providing a calendar (year, month, date, day, hour, minute, second) function and a clock counter function, this module provides an abundance of other functions including an alarm function, fixed-cycle timer function, time update interrupt function, and 32.768 kHz output function.
  • Page 5: Terminal Description

    Signal name Input This is the serial clock input pin for I This pin's signal is used for input and output of address, data, and ACK bits, synchronized with the serial clock used for I Since the SDA pin is an N-ch open drain pin during output, be sure to connect a suitable pull-up resistance relative to the signal line capacity.
  • Page 6: Absolute Maximum Ratings

    OUT1 Output voltage (2) OUT2 Storage temperature 5. Recommended Operating Conditions Item Symbol Operating supply voltage Temp. compensation voltage Clock supply voltage Operating temperature 6. Frequency Characteristics Item Symbol Δ f / f Frequency stability Frequency/voltage f / V characteristics...
  • Page 7: Electrical Characteristics

    RX − 8801 SA / JE 7. Electrical Characteristics 7.1. DC Characteristics Item Symbol Current consumption (1) FOE = GND Current FOUT : output OFF ( High Z ) consumption (2) Compensation interval 2.0 s Current consumption (3) FOE = V FOUT :32.768 kHz, CL =0pF Current Compensation interval 2.0 s...
  • Page 8: Ac Characteristics

    RX − 8801 SA / JE 7.2. AC Characteristics Item SCL clock frequency Start condition setup time Start condition hold time Data setup time Data hold time Stop condition setup time Bus idle time between start condition and stop condition Time when SCL "L"...
  • Page 9: Use Methods

    The 32.768-kHz clock (with precision equal to that of the built-in crystal oscillator) can be output via the FOUT pin. The FOUT pin is a CMOS output pin which can be set for clock output when the FOE pin is at high level and for low-level output when the FOE pin is at high impedance.
  • Page 10: Description Of Registers

    When after the initial power-up or when the result of read out the VLF bit is "1" , initialize all registers, before using the module. Be sure to avoid entering incorrect date and time data, as clock operations are not guaranteed when the data or time data is incorrect.
  • Page 11: Control Register (Reg F)

    ∗3) "−" indicates no default value has been defined. • This register is used to control interrupt event output from the /INT pin and the stop/start status of clock and calendar operations. 1) CSEL0,1 ( Compensation interval Select 0, 1 ) bits The combination of these two bits is used to set the temperature compensation interval.
  • Page 12 If a STOP-condition or repeated START-condition(I operating, stop status is automatically canceled (the RESET bit value is changed from "1" to "0"). ∗ For optimum performance, do not use this bit for functions other than the clock and calendar functions. Data...
  • Page 13: Flag Register (Reg-E)

    4) VLF ( Voltage Low Flag ) bit This flag bit indicates the retained status of clock operations or internal data. Its value changes from "0" to "1" when data loss occurs, such as due to a supply voltage drop. Once this flag bit's value is "1", its value is retained until a "0"...
  • Page 14: Extension Register (Reg-D)

    (bit 3) Write/Read 6) TSEL0,1 ( Timer Select 0, 1 ) bits The combination of these two bits is used to set the countdown period (source clock) for the fixed-cycle timer interrupt function (four settings can be made). TSEL1 TSEL0,1...
  • Page 15: Ram Register (Reg - 7)

    • The clock counter counts seconds, minutes, and hours. • The data format is BCD format seconds. ∗ Note with caution that writing non-existent time data may interfere with normal operation of the clock counter. 1) Second counter Address Function •...
  • Page 16: Calendar Counter (Reg 4 To 6)

    RX − 8801 SA / JE 8.2.8. Calendar counter (Reg 4 to 6) Address Function MONTH YEAR ∗) "o" indicates write-protected bits. A zero is always read from these bits. • The auto calendar function updates all dates, months, and years from January 1, 2001 to December 31, 2099. •...
  • Page 17: Fixed-Cycle Timer Interrupt Function

    (1) When a "1" is written to the TE bit, the fixed-cycle timer countdown starts from the preset value. (2) A fixed-cycle timer interrupt event starts a countdown based on the countdown period (source clock). When the count value changes from 001h to 000h, an interrupt event occurs.
  • Page 18: Related Registers For Function Of Time Update Interrupts

    This register is used to set the default (preset) value for the counter. Any count value from 1 (001 h) to 4095 (FFFh) can be set. The counter counts down based on the source clock's period, and when the count value changes from 001h to 000h, the TF bit value becomes "1".
  • Page 19: Fixed-Cycle Timer Interrupt Interval (Example)

    A time error in the fixed-cycle timer will produce a positive or negative time period error in the selected source clock. The fixed-cycle timer's time is within the following range relative to the time setting. (Fixed-cycle timer's time setting (∗) − source clock period) to (timer's time setting) ∗...
  • Page 20: Time Update Interrupt Function

    Operation in RTC Write operation (1) A time update interrupt event occurs when the internal clock's value matches either the second update time or the minute update time. The USEL bit's specification determines whether it is the second update time or the minute update time that must be matched.
  • Page 21: Related Registers For Time Update Interrupt Functions

    RX − 8801 SA / JE 8.4.2. Related registers for time update interrupt functions. Address Function Extension Register Flag Register Control Register ∗ ) "o" indicates write-protected bits. A zero is always read from these bits. ∗ Before entering settings for operations, we recommend writing a "0" to the UIE bit to prevent hardware interrupts from occurring inadvertently while entering settings.
  • Page 22: Alarm Interrupt Function

    RX − 8801 SA / JE 8.5. Alarm Interrupt Function The alarm interrupt generation function generates interrupt events for alarm settings such as date, day, hour, and minute settings. When an interrupt event occurs, the AF bit value is set to "1" and the /INT pin goes to low level to indicate that an event has occurred.
  • Page 23: Related Registers

    RX − 8801 SA / JE 8.5.2. Related registers Address Function HOUR WEEK MIN Alarm HOUR Alarm WEEK Alarm DAY Alarm Extension Register Flag Register Control Register ∗ 1) "o" indicates write-protected bits. A zero is always read from these bits. ∗...
  • Page 24: Examples Of Alarm Settings

    RX − 8801 SA / JE 3) AF (Alarm Flag) bit When this flag bit value is already set to "0", occurrence of an alarm interrupt event changes it to "1". When this flag bit value is "1", its value is retained until a "0" is written to it. Data Write Read...
  • Page 25: Reading/Writing Data Via The I 2 C Bus Interface

    C-BUS The I C bus supports bi-directional communications via two signal lines: the SDA (data) line and SCL (clock) line. A combination of these two signals is used to transmit and receive communication start/stop signals, data transfer signals, acknowledge signals, and so on.
  • Page 26: Starting And Stopping I C Bus Communications

    RX − 8801 SA / JE 8.6.3. Starting and stopping I C bus communications START condition [ S ] 1) START condition, repeated START condition, and STOP condition (1) START condition • The SDA level changes from high to low while SCL is at high level. (2) STOP condition •...
  • Page 27: Data Transfers And Acknowledge Responses During I 2 C-Bus Communications

    ACK signal.) Immediately after the falling edge of the clock pulse corresponding to the 8th bit of data on the SCL line, the transmitter releases the SDA line and the receiver sets the SDA line to low (= acknowledge) level.
  • Page 28: I 2 C Bus Protocol

    RX − 8801 SA / JE 8.6.6. I C bus protocol In the following sequence descriptions, it is assumed that the CPU is the master and the RX-8801 is the slave. a. Address specification write sequence Since the RX-8801 includes an address auto increment function, once the initial address has been specified, the RX-8801 increments (by one byte) the receive address each time data is transferred.
  • Page 29: Backup And Recovery

    8.7. Backup and Recovery Item Symbol Power supply detection voltage ( 1 ) Power supply detection voltage ( 2 ) Power supply drop time Initial power-up time Clock maintenance power-up time Back up Condition Min. − − − − 1.6V → V ≤...
  • Page 30: Connection With Typical Microcontroller

    Note : It uses the secondary battery or a lithium battery. When using the seconding battery, the diode is not required. When using the lithium battery, the diode is required. For detailed value on the resistance, please consult a battery maker. 8.9. When used as a clock source (32 kHz-TCXO) 32.768kHz D1: Schottky Barrier...
  • Page 31: External Dimensions / Marking Layout

    RX − 8801 SA / JE 9. External Dimensions / Marking Layout 9.1. RX − 8801 SA ( SOP − 14pin ) 9.1.1. External dimensions RX − 8801 SA ( SOP − 14pin ) • External dimensions 10.1 ± 5.0 7.4 0.05 Min.
  • Page 32 RX − 8801 SA / JE 9.2. RX − 8801 JE ( VSOJ − 20pin ) 9.2.1. External dimensions RX − 8801 JE ( VSOJ − 20pin ) • External dimensions 7.0 ± 0.3 1.3 1.5 Max. 0 Min. 0.22 0.65 0.12 ∗...
  • Page 33: Application Notes

    RX − 8801 SA / JE 10. Application notes 1) Notes on handling This module uses a C-MOS IC to realize low power consumption. Carefully note the following cautions when handling. (1) Static electricity While this module has built-in circuitry designed to protect it against electrostatic discharge, the chip could still be damaged by a large discharge of static electricity.
  • Page 34 EPSON HONG KONG LTD. 20/F., Harbour Centre, 25 Harbour Road, Wanchai,Hong kong Phone: (852) 2585-4600 Fax: (852) 2827-2152 EPSON TAIWAN TECHNOLOGY & TRADING LTD. 14F, No.7, Song Ren Road, Taipei 110 Phone: (886) 2-8786-6688 Fax: (886)2-8786-6660 EPSON SINGAPORE PTE. LTD.

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