Rainbow-electronics DS1554 Manual do Utilizador descarregar pdf (Página 8)

DS1554

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ALARM MASK BITS Table 3

AM4 AM3 AM2 AM1 ALARM RATE

1111Once per second

1110When seconds match

1100When minutes and seconds match

1000When hours, minutes, and seconds match

0000When date, hours, minutes, and seconds match

When the RTC Register values match Alarm Register settings, the Alarm Flag bit (AF) is set to a 1. If

Alarm Flag Enable (AE) is also set to a 1, the alarm condition activates the IRQ /FT pin. The IRQ /FT

signal is cleared by a read or write to the Flags Register (Address 7FF0h) as shown in Figure 2 and 3.

When CE is active, the IRQ /FT signal may be cleared by having the address stable for as short as 15 ns

and either OE or WE active, but is not guaranteed to be cleared unless t

is fulfilled. The alarm flag is

also cleared by a read or write to the Flags Register but the flag will not change states until the end of the

read/write cycle and the IRQ /FT signal has been cleared.

CLEARING IRQ WAVEFORMS Figure 2

CLEARING IRQ WAVEFORMS Figure 3

CE,

CE=0

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 19 20

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Rainbow-electronics DS1554 Manual do Utilizador Página 8