DS1689/DS1693

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REGISTER C

MSB

LSB

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

IRQF

PF

AF

UF

0

0

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

WF = WIE = 1

AF = AIE = 1

KF = KSE = 1

UF = UIE = 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

LSB

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

VRT

0

0

0

0

0

0

0

Bit 7: VRT (Valid RAM and Time). This bit indicates the condition of the battery connected to the

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.