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. Before entering settings for operations, we recommend writing a "0" to the AIE bit to prevent hardware interrupts from occurring inadvertently while entering settings. . When the STOP bit or RESET bit value is "1" alarm interrupt events do not occur. . When the alarm interrupt function is not being used, the Alarm registers (Reg - 8 to A) can be used as a RAM register. In such cases, be sure to write "0" to the AIE bit. . When the AIE bit value is "1" and the Alarm registers (Reg - 8 to A) is being used as a RAM register, /INT may be changed to low level unintentionally. 1) WADA (Week Alarm /Day Alarm) bit The alarm interrupt function uses either "Day" or "Week" as its target. The WADA bit is used to specify either WEEK or DAY as the target for alarm interrupt events. WADA Data Description Write/Read 0 Sets WEEK as target of alarm function (DAY setting is ignored) 1 Sets DAY as target of alarm function (WEEK setting is ignored) 2) Alarm registers (Reg - 8 to A) bit 0 1 1 0 1 The hour, minute, date or day when an alarm interrupt event will occur is set using this register and the WADA bit. In the WEEK alarm /Day alarm register (Reg - A), the setting selected via the WADA bit determines whether WEEK alarm data or DAY alarm data will be set. If WEEK has been selected via the WADA bit, multiple days can be set (such as Monday, Wednesday, Friday, Saturday). When the settings made in the alarm registers and the WADA bit match the current time, the AF bit value is changed to "1". At that time, if the AIE bit value has already been set to "1", the /INT pin goes low. .1) The register that "1" was set to "AE" bit, doesn't compare alarm. (Example) Write 80h (AE = "1") to the WEEK Alarm /DAY Alarm register (Reg - A): Only the hour and minute settings are used as alarm comparison targets. The week and date settings are not used as alarm comparison targets. As a result, alarm occurs if only an hour and minute accords with alarm data. .2) If all three AE bit values are "1" the week/date settings are ignored and an alarm interrupt event will occur once per minute. Page - 19 MQ372-02 RX -8581 SA /JE/NB 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. AF Data Description Write 0 The AF bit is cleared to zero to prepare for the next status detection . Clearing this bit to zero enables /INT low output to be canceled (/INT remains Hi-Z) when an alarm interrupt event has occurred. 1 This bit is invalid after a "1" has been written to it. Read 0 Alarm interrupt events are not detected. 1 Alarm interrupt events are detected. (Result is retained until this bit is cleared to zero.) 4) AIE (Alarm Interrupt Enable) bit When an alarm interrupt event occurs (when the AF bit value changes from "0" to "1"), this bit's value specifies whether an interrupt signal is generated (/INT status changes from Hi-Z to low) or is not generated (/INT status remains Hi-Z). AIE Data Description Write/Read 0 1) When an alarm interrupt event occurs, an interrupt signal is not generated or is canceled (/INT status remains Hi-Z). 2) When an alarm interrupt event occurs, the interrupt signal is canceled (/INT status changes from low to Hi-Z). . Even when the AIE bit value is "0" another interrupt event may change the /INT status to low (or may hold /INT = "L"). 1 When an alarm interrupt event occurs, an interrupt signal is generated (/INT status changes from Hi-Z to low). . When an alarm interrupt event occurs, low-level output from the /INT pin occurs only when the AIE bit value is "1". This value is retained (not automatically cleared) until the AF bit is cleared to zero. 8.5.2. Examples of alarm settings 1) Example of alarm settings when "Day" has been specified (and WADA bit = "0") Day is specified WADA bit = "0" Reg – A Reg - 9 Reg - 8 bit 7 AE bit 6 S bit 5 F bit 4 T bit 3 W bit 2 T bit 1 M bit 0 S HOUR Alarm MIN Alarm Monday through Friday, at 7:00 AM . Minute value is ignored 0 0 1 1 1 1 1 0 07 h 80 h . FF h Every Saturday and Sunday, for 30 minutes each hour . Hour value is ignored 0 1 0 0 0 0 0 1 80 h . FF h 30 h Every day, at 6:59 AM 0 1 1 . 1 1 . . 1 1 . . 1 . 1 . 18 h 59 h .: Don't care 2) Example of alarm settings when "Day" has been specified (and WADA bit = "1") Day is specified WADA bit = "1" Reg - A Reg - 9 Reg - 8 bit 7 AE bit 6 • bit 5 20 bit 4 10 bit 3 08 bit 2 04 bit 1 02 bit 0 01 HOUR Alarm MIN Alarm First of each month, at 7:00 AM . Minute value is ignored 0 0 0 0 0 0 0 1 07 h 80 h . FF h 15th of each month, for 30 minutes each hour . Hour value is ignored 0 0 0 1 0 1 0 1 80 h . FF h 30 h Every day, at 6:59 PM 1 . . . . . . . 18 h 59 h .: Don't care Page - 20 MQ372-02 RX -8581 SA /JE/NB 8.6. Reading/Writing Data via the I2C Bus Interface 8.6.1. Overview of I2C-BUS The I2C bus supports bi-directional communications via two signal lines: the SDA (data) line and SCL (clock)...

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