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14 page 
���������������������������������������������������������������� Maxim Integrated Products 14 DS3232M ±5ppm, I2C Real-Time Clock with SRAM Alarms The device contains two time-of-day/date alarms. Alarm 1 can be set by writing to registers 07h–0Ah. Alarm 2 can be set by writing to registers 0Bh–0Dh. See Table 2. The alarms can be programmed (by the alarm enable and INTCN bits in the Control register) to activate the INT/SQW output on an alarm match condition. Bit 7 of each of the time-of-day/date alarm registers are mask bits (Table 2). When all the mask bits for each alarm are logic 0, an alarm only occurs when the values in the timekeeping registers match the corresponding values stored in the time-of-day/date alarm registers. The alarms can also be programmed to repeat every second, minute, hour, day, or date. Table 3 shows the possible settings. Configurations not listed in the table result in illogical operation. The DY/DT bits (bit 6 of the alarm day/date registers) con- trol whether the alarm value stored in bits 0–5 of that register reflects the day of the week or the date of the month. If DY/DT is written to logic 0, the alarm is the result of a match with date of the month. If DY/DT is written to logic 1, the alarm is the result of a match with day of the week. When the RTC register values match alarm register settings, the corresponding alarm flag A1F or A2F bit is set to logic 1. If the correspond- ing alarm interrupt enable A1IE or A2IE bit is also set to logic 1, the alarm condition activates the INT/SQW signal if the INTCN bit is set to logic 1. The match is tested on the once-per-second update of the time and date registers. Table 3. Alarm Mask Bits DY/DT ALARM 1 REGISTER MASK BITS (BIT 7) ALARM RATE A1M4 A1M3 A1M2 A1M1 X 1 1 1 1 Alarm once a second X 1 1 1 0 Alarm when seconds match X 1 1 0 0 Alarm when minutes and seconds match X 1 0 0 0 Alarm when hours, minutes, and seconds match 0 0 0 0 0 Alarm when date, hours, minutes, and seconds match 1 0 0 0 0 Alarm when day, hours, minutes, and seconds match DY/DT ALARM 2 REGISTER MASK BITS (BIT 7) ALARM RATE A2M4 A2M3 A2M2 X 1 1 1 Alarm once per minute (00 seconds of every minute) X 1 1 0 Alarm when minutes match X 1 0 0 Alarm when hours and minutes match 0 0 0 0 Alarm when date, hours, and minutes match 1 0 0 0 Alarm when day, hours, and minutes match |
