English
Language : 

DS1689_05 Datasheet, PDF (15/36 Pages) Dallas Semiconductor – 3V/5V Serialized Real-Time Clocks with NV RAM Control
◁
REGISTER C
MSB
BIT 7
BIT 6
IRQF
PF
BIT 5
AF
BIT 4
UF
BIT 3
0
BIT 2
0
DS1689/DS1693
BIT 1
0
LSB
BIT 0
0
Bit 7: IRQF (Interrupt Request Flag). This bit is set to 1 when one or more of the following are true:
PF = PIE = 1
AF = AIE = 1
UF = UIE = 1
WF = WIE = 1
KF = KSE = 1
RF = RIE = 1
i.e., IRQF = (PF • PIE) + (AF • AIE) + (UF • UIE) + (WF • WIE) + (KF • KSE) + (RF • RIE)
Any time the IRQF bit is 1, the IRQ pin is driven low. Flag bits PF, AF, and UF are cleared after Register
C is read by the program.
Bit 6: PF (Periodic Interrupt Flag). This bit is a read-only bit that is set to a 1 when an edge is detected
on the selected tap of the divider chain. The RS3–RS0 bits establish the periodic rate. PF is set to 1
independent of the state of the PIE bit. When both PF and PIE are 1s, the IRQ signal is active and will set
the IRQF bit. The PF bit is cleared by a software read of Register C.
Bit 5: AF (Alarm Interrupt Flag). A 1 in the AF bit indicates that the current time has matched the
alarm time. If the AIE bit is also 1, the IRQ pin goes low and a 1 appears in the IRQF bit. A read of
Register C clears AF.
Bit 4: UF (Update-Ended Interrupt Flag). This bit is set after each update cycle. When the UIE bit is
set to 1, the 1 in UF causes the IRQF bit to be 1, which asserts the IRQ pin. UF is cleared by reading
Register C.
Bits 3 to 0: Unused. These bits always read 0 and cannot be written.
REGISTER D
MSB
BIT 7
BIT 6
VRT
0
BIT 5
0
BIT 4
0
BIT 3
0
BIT 2
0
BIT 1
0
LSB
BIT 0
0
Bit 7: VRT (Valid RAM and Time). This bit indicates the condition of the battery connected to the
VBAT pin or the battery connected to VBAUX, whichever is at a higher voltage. This bit is not writable and
should always be a 1 when read. If a 0 is ever present, an exhausted lithium energy source is indicated
and both the contents of the RTC data and RAM data are questionable.
Bits 6 to 0: Unused. These bits cannot be written and always read 0 when read.
15 of 36
 ▷