DS1689 Datasheet, PDF (13/32 Pages) Dallas Semiconductor – 3-Volt/5-Volt Serialized Real-Time Clock with NV RAM Control

REGISTER B
MSB
BIT 7
BIT 6
SET
PIE
BIT 5
AIE
BIT 4
UIE
BIT 3
SQWE
BIT 2
DM
DS1689/DS1693
BIT 1
24/12
LSB
BIT 0
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 internal functions of the
DS1689/DS1693.
PIE - The Periodic Interrupt Enable 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 DS1689/DS1693 functions.
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 3 time bytes
equal the 3 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 internal functions of the DS1689/DS1693 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 SET bit going high clears the 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 and the E32K bit is driven out on the SQW pin. When the
SQWE bit is set to 0, the SQW pin is held low. 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. 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.
DSE - The Daylight Savings Enable (DSE) bit is a read/write bit which enables two special updates when
DSE is set to 1. On the first Sunday in April the time increments from 1:59:59 am to 3:00:00 AM. On the
last Sunday in October when the time first reaches 1:59:59 AM it changes to 1:00:00 AM. These special
updates do not occur when the DSE bit is a 0. This bit is not affected by internal functions.
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