DS12C887 데이터 시트보기 (PDF) - Dallas Semiconductor -> Maxim Integrated

부품명

상세내역

일치하는 목록

DS12C887

Real Time Clock

Dallas Semiconductor -> Maxim Integrated 

DS12C887

POWER-DOWN/POWER-UP CONSIDERATIONS

The Real Time Clock function will continue to operate and all of the RAM, time, calendar, and alarm

memory locations remain nonvolatile regardless of the level of the VCC input. When VCC is applied to the

DS12C887 and reaches a level of greater than 4.25 volts, the device becomes accessible after 200 ms,

provided that the oscillator is running and the oscillator countdown chain is not in reset (see Register A).

This time period allows the system to stabilize after power is applied. When VCC falls below 4.25 volts,

the chip select input is internally forced to an inactive level regardless of the value of CS at the input pin.

The DS12C887 is, therefore, write-protected. When the DS12C887 is in a write-protected state, all inputs

are ignored and all outputs are in a high impedance state. When VCC falls below a level of approximately

3 volts, the external VCC supply is switched off and an internal lithium energy source supplies power to

the Real Time Clock and the RAM memory.

RTC ADDRESS MAP

The address map for the DS12C885 is shown in Figure 2. The address map consists of 113 bytes of user

RAM, 11 bytes of RAM that contain the RTC time, calendar, and alarm data, and 4 bytes which are used

for control and status. All 128 bytes can be directly written or read except for the following:

1. Registers C and D are read-only.

2. Bit-7 of Register A is read-only.

3. The high order bit of the seconds byte is read-only.

DS12C887 REAL TIME CLOCK ADDRESS MAP Figure 2

5 of 19

Share Link: