DS12887 REGISTER B MSB LSB BIT7 BIT6 BIT5 BIT 4 BIT3 BIT2 BIT 1 BIT0 SET PIE AIE UIE SQWE DM 24/12 DSE SET When the set bit is a o the update transfer functions normally by advancing the counts or per second When the ET bit is written to a any update transfer is inhibited and the program can initialize the time and calendar bytes without an update occurring in the midst of initializing.Read cycles can be executed in a similar manner.SET is a read/write bit that is not modified by RESET or intemal functions of the DS12887. PIE The periodic interrupt enable PIE bit is a read/write bit which allows the Periodic Interrupt Flag(PF)bit in Register C to drive the IRQ pin low.When the PIE bit is set to 1,periodic interrupts are generated by driving the RQ pin low at a rate specified by the RS3-RS0 bits of Register A.A0in the PIE bit blocks the IRQ output from being driven by a periodic interrupt,but the Periodic Flag(PF)bit is still set at the periodic rate.PIE is not modified by any internal DS12887 functions,but is cleared to 0 on RESET AIE The Alarm Interrupt Enable(AIE)bit is a read/write bit which,when set to a 1,permits the Alarm Flag (AF)bit in Register C to assert IRQ.An alarm interrupt occurs for each second that the three time bytes equal the three alarm bytes including a"don't care"alarm code of binary 11XXXXXX.When the AlE bit is AF bit does not initiate the R signal.The RESET pin clears AIE to The interal functions of the DS12887 do not affect the AlE bit. UIE The Update Ended Interrupt Enable(UIE)bit is a read/write that enables the Update End Flag(UF)bit in Register C to assert IRQ.The RESET pin going low or the SET bit going high clears to UlE bit. SQWE When the Squ SQW pin is held low,the state of SQWE is cleared by the RESET pin.SQWE is a read/write bit. DM modified by internal functions or RESET.A 1 in DM signifies binary data while a 0 in DM specifies Binary Coded Decimal (BCD)data 24/12 The 24/12 control bit establishes the format of the hours byte.A 1 indicates the 24-hour mode and a 0 indicates the 12-hour mode.This bit is read/write and is not affected by internal functions of RESET. 10of19DS12887 10 of 19 REGISTER B MSB LSB BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 SET PIE AIE UIE SQWE DM 24/12 DSE SET When the SET bit is a 0, the update transfer functions normally by advancing the counts once per second. When the SET bit is written to a 1, any update transfer is inhibited and the program can initialize the time and calendar bytes without an update occurring in the midst of initializing. Read cycles can be executed in a similar manner. SET is a read/write bit that is not modified by RESET or internal functions of the DS12887. PIE The periodic interrupt enable PIE bit is a read/write bit which allows the Periodic Interrupt Flag (PF) bit in Register C to drive the IRQ pin low. When the PIE bit is set to 1, periodic interrupts are generated by driving the IRQ pin low at a rate specified by the RS3–RS0 bits of Register A. A 0 in the PIE bit blocks the IRQ output from being driven by a periodic interrupt, but the Periodic Flag (PF) bit is still set at the periodic rate. PIE is not modified by any internal DS12887 functions, but is cleared to 0 on RESET . AIE The Alarm Interrupt Enable (AIE) bit is a read/write bit which, when set to a 1, permits the Alarm Flag (AF) bit in Register C to assert IRQ . An alarm interrupt occurs for each second that the three time bytes equal the three alarm bytes including a “don’t care” alarm code of binary 11XXXXXX. When the AIE bit is set to 0, the AF bit does not initiate the IRQ signal. The RESET pin clears AIE to 0. The internal functions of the DS12887 do not affect the AIE bit. UIE The Update Ended Interrupt Enable (UIE) bit is a read/ write that enables the Update End Flag (UF) bit in Register C to assert IRQ . The RESET pin going low or the SET bit going high clears to UIE bit. SQWE When the Square Wave Enable (SQWE) bit is set to a 1, a square wave signal at the frequency set by the rate–selection bits RS3 through RS0 is driven out on a SQW pin. When the SQWE bit is set to z0, the SQW pin is held low; the state of SQWE is cleared by the RESET pin. SQWE is a read/write bit. DM The Data Mode (DM) bit indicates whether time and calendar information is in binary or BCD format. The DM bit is set by the program to the appropriate format and can be read as required. This bit is not modified by internal functions or RESET . A 1 in DM signifies binary data while a 0 in DM specifies Binary Coded Decimal (BCD) data. 24/12 The 24/12 control bit establishes the format of the hours byte. A 1 indicates the 24–hour mode and a 0 indicates the 12–hour mode. This bit is read/write and is not affected by internal functions of RESET