Rainbow-electronics DS1558Y Instrukcja Użytkownika Pobierz pdf (Strona 3)

DS1558

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programmed limits. The DS1558 power-on reset can be used to detect a system power-down or failure

and hold the CPU in a safe reset state until normal power returns and stabilizes; the RST output is used

for this function.

The DS1558 also contains its own power-fail circuitry, which automatically protects the data in the clock

and SRAM against out-of-tolerance V

CCI

conditions by inhibiting the CE input when the V

supply

enters an out-of-tolerance condition. When V

CCI

goes below the level of V

BAT

, the external battery is

switched on to supply energy to the clock and the external SRAM. This feature provides a high degree of

data security during unpredictable system operation brought on by low V

levels.

Figure 1. BLOCK DIAGRAM

Note: Any unused upper address pins must be connected to V

to properly address the RTC.

SIGNAL DESCRIPTIONS

A0–A18 – Address inputs for address decode. The DS1558 uses the address inputs to determine whether

or not a read or write cycle should be directed to the attached SRAM or to the RTC registers.

DQ0–DQ7 – Data input/output pins for the RTC registers.

IRQ /FT – This pin is used to output the alarm interrupt or the frequency test signal. It is open drain and

requires an external pullup resistor.

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Rainbow-electronics DS1558Y Instrukcja Użytkownika Strona 3