Rainbow-electronics DS12887 Manual de usuario descargar pdf (Pagina 13)

DS12887

13 of 19

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

IRQF– The interrupt request flag (IRQF) bit is set to a 1 when one or more of the following are true:

PF = PIE = 1

AF = AIE = 1

UF = UIE = 1

That is, IRQF = PF x PIE + AF x AIE + UF x UIE.

Any time the IRQF bit is a 1, the IRQ pin is driven low. All flag bits are cleared after Register C is read

by the program or when the RESET pin is low.

PF– The periodic-interrupt flag (PF) 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 through RS0 bits establish the periodic rate. PF is set to a 1

independent of the state of the PIE bit. When both PF and PIE are 1s, the IRQ signal is active and sets the

IRQF bit. The PF bit is cleared by a RESET or a software read of Register C.

AF– A 1 in the alarm-interrupt flag (AF) bit indicates that the current time has matched the alarm time. If

the AIE bit is also a 1, the IRQ pin goes low and a 1 appears in the IRQF bit. A RESET or a read of

UF – The update-ended interrupt flag (UF) bit is set after each update cycle. When the UIE bit is set to 1,

the one in UF causes the IRQF bit to be a 1, which asserts the IRQ pin. UF is cleared by reading Register

C or a RESET .

BIT 0, BIT 1, BIT 2, BIT 3 – These are unused bits of the status Register C. These bits always read 0

and cannot be written.

MSB LSB

BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

VRT0000000

VRT – The valid RAM and time (VRT) bit is set to the 1 state prior to shipment. This bit is not writable

and should always be a 1 when read. If a 0 is ever present, an exhausted internal lithium energy source is

indicated and both the contents of the RTC data and RAM data are questionable. This bit is unaffected by

RESET .

BIT 6, BIT 5, BIT 4, BIT 3, BIT 2, BIT 1, BIT 0– The remaining bits of Register D are not usable.

They cannot be written and, when read, they always read 0.

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Rainbow-electronics DS12887 Manual de usuario Pagina 13