Epson RX-8581JE Applications Manual
Epson RX-8581JE Applications Manual

Epson RX-8581JE Applications Manual

Real time clock module


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Real Time Clock Module
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Summary of Contents for Epson RX-8581JE

  • Page 1 MQ372-02 Application Manua Real Time Clock Module RX-8581SA/JE/NB Model RX-8581SA RX-8581JE RX-8581NB Product Number Q4185815xxxxx00 Q4185817xxxxx00 Q4185819xxxxx00...
  • Page 2 • The information, applied circuit, program, using way etc., written in this material is just for reference. Seiko Epson does not assume any liability for the occurrence of infringing any patent or copyright of third party. This material does not authorize the licence for any patent or intellectual property rights.
  • Page 3: Table Of Contents

    RX - 8581 SA 1. Overview ...1 2. Block Diagram ...1 3. Terminal description 3.1. Terminal connections 3.2. Pin Functions 4. Absolute Maximum Ratings 5. Recommended Operating Conditions 6. Frequency Characteristics 7. Electrical Characteristics 7.1. DC characteristics 7.2. AC Characteristics 8.
  • Page 4: Overview

    C bus interface-compliant real-time clock which includes a 32.768-kHz crystal oscillator. 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

    3.2. Pin Functions Signal name 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

    Input voltage (2) Output voltage (1) OUT1 Output voltage (2) OUT2 Storage temperature 5. Recommended Operating Conditions Item Symbol Operating supply voltage Clock supply voltage Operating temperature 6. Frequency Characteristics Item Symbol Frequency precision f /f Frequency/voltage f /V characteristics...
  • Page 7: Ac Characteristics

    RX - 8581 SA 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 8: 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 low level.
  • Page 9: 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 10 "o" indicates write-protected bits. A zero is always read from these bits. " " 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.
  • Page 11 Writing a "1" to this bit stops the counter operations. Writing a "0" to this bit cancels stop status (restarts operations). For optimum performance, do not use this bit for functions other than the clock and calendar functions. Data STOP...
  • Page 12 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 13 This bit is used to specify either "second update" or "minute update" as the update generation timing of the time update interrupt function. Writing a "1" to this bit specifies the internal clock's "minute update" (once per minute) operation as the timing by which time update interrupts are generated.
  • Page 14 "o" indicates write-protected bits. A zero is always read from these bits. 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 This second counter counts from "00"...
  • Page 15 RX - 8581 SA 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. The data format is BCD format.
  • Page 16: 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 17 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 18 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 ( )
  • Page 19: 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 20 RX - 8581 SA 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 21: Alarm Interrupt Function

    RX - 8581 SA 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 22 RX - 8581 SA 8.5.2. Related registers Address Function HOUR WEEK MIN Alarm HOUR Alarm WEEK Alarm DAY Alarm Extension Register Flag Register Control Register "o" indicates write-protected bits. A zero is always read from these bits. Bits marked with " " are RAM bits that can contain any value and are read/write-accessible. Before entering settings for operations, we recommend writing a "0"...
  • Page 23 RX - 8581 SA 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 24: Reading/Writing Data Via The I 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 25 RX - 8581 SA 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 This condition regulates how communications on the I 2 C-BUS are terminated.
  • Page 26 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 27 RX - 8581 SA 8.6.6. I C bus protocol In the following sequence descriptions, it is assumed that the CPU is the master and the RX-8581 is the slave. a. Address specification write sequence Since the RX-8581 includes an address auto increment function, once the initial address has been specified, the RX-8581 increments (by one byte) the receive address each time data is transferred.
  • Page 28: Backup And Recovery

    RX - 8581 SA 8.7. Backup and Recovery Item Power supply drop time Initial power-up time Clock maintenance power-up time 8.8. Connection with Typical Microcontroller SLAVE ADRS = 1010 001 C-BUS Back up Symbol Min. 2 s /V 1 s /V...
  • Page 29: External Dimensions / Marking Layout

    RX - 8581 SA 9. External Dimensions / Marking Layout RX-8581 SA (SOP - 14 pin) External dimensions 10.1 0.2 R8581 E 1234A 0.35 1.27 The crystal oscillator's metal case may be visible in the area (on top) indicated in broken lines but this has no effect on the device's characteristics.
  • Page 30: Reference Data

    Typ. 1. Frequency and temperature characteristics can be approximated using the following equations. +100 2. To determine overall clock accuracy, add the frequency precision and voltage characteristics. f/f = f/fo : Frequency precision 3. How to find the date difference...
  • Page 31: Application Notes

    RX - 8581 SA 11. Application notes 11.1. 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 32 EPSON HONG KONG LTD. 20/F., Harbour Centre, 25 Harbour Road, Wanchai, Hong kong Phone: (852) 2585-4600 Fax: (852) 2827-2152 EPSON ELECTRONIC TECHNOLOGY DEVELOPMENT (SHENZHEN )CO., LTD. 12/F, Dawning Mansion,#12 Keji South Road, Hi-Tech Park, Shenzhen, China Phone EPSON TAIWAN TECHNOLOGY & TRADING LTD.

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