ACT5880 datasheet(77/87 Pages) ACTIVE-SEMI

77 / 87 page

ACT5880

Rev 2, 03-Sep-13

- 77 -

www.active-semi.com

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I2CTM is a trademark of NXP.

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To clear the RTC wake-up alarm interrupt:

Set bit nWKALM[ ] = 1 ;

Read byte 0x3C;

Read byte 0x3D.

To disable the RTC wake-up alarm:

Set bit nWKALM[ ] = 1;

Set bit RAAI[ ] = 0.

And every change interrupt is also available in the

ACT5880, enabled by setting respective register bits

of the RDAI[ ], RHAI[ ], RMAI[ ] and RSAI[ ]. This

functions helps in maintaining the clock display

refresh against the day counts changes, the hour

counts changes, the minute counts changes and the

second counts changes. When the every change

happens, the interrupt output is kept for 0.5s for

second change, for 1s for minute change, hour

change and day change. Resetting respective

enabling bit to 0 clears the interrupt output

immediately.

Oscillator Square Wave Output

The CLK32 is the shaped output of the oscillator, an

open-drain output that requires an external pull-up

resistor. The pull-up resistor is pulled-up to the same

rail that powers the circuit that wants the clock input,

is easy for logic level interfacing between the RTC

circuit and the system. The pull-up resistance is

selected against the edge slope rate wanted and the

parasitic capacitance of the connection, which is

typically in range of 7pF to 35pF for pins and normal

trace width of 5mil to 10mil and length of 400mil to

1000mil. Typically, a 300k resistance is the highest

volume acceptable to most systems and placing the

resistor close to the input pin provides slightly better

performance. Refer to Figure 14 for the circuit

diagram.

Figure 14:

The Output Circuit of the CLK32 Output.

ACT5880

CLK32

System

RDDW

System VCC

(Placed close

to input side )

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