CDP68HC68T1(1997) 데이터 시트보기 (PDF) - Intersil

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CDP68HC68T1
(Rev.:1997)

CMOS Serial Real-Time Clock With RAM and Power Sense/Control

Intersil 

CDP68HC68T1

XTAL IN

INT

INT

XTAL OUT

VDD

0V

LINE

CPU

CDP68HC05C16B

VDD

REAL-TIME CLOCK

CDP68HC68T1

I

STATUS REGISTER

FIGURE 3. POWER-SENSING FUNCTIONAL DIAGRAM

FROM SYSTEM

POWER

TO SYSTEM

POWER CONTROL

VSYS

I

INTERRUPT

CONTROL

REGISTER

SERIAL

INTERFACE

PSE

CLK

OUT

CPUR

OSC

RESET

MISO

MOSI

REAL-TIME CLOCK

CDP68HC68T1

CPU

CDP68HC05C4B

FIGURE 4. POWER-DOWN FUNCTIONAL DIAGRAM

POWER

UP

POWER

SENSE

OR

ALARM

CIRCUIT

PERIODIC

INTERRUPT

SIGNAL

SERIAL

INTERFACE

REAL-TIME CLOCK

CDP68HC68T1

PSE

CPUR

CLK

OUT

INT

MISO

MOSI

FIGURE 5. POWER-UP FUNCTIONAL DIAGRAM (INITIATED

BY INTERRUPT SIGNAL

Power Sensing (See Figure 3)

When Power Sensing is enabled (Bit 5 = 1 in Interrupt Con-

trol Register), AC transitions are sensed at the LINE input pin.

Threshold detectors determine when transitions cease. After

a delay of 2.68ms to 4.64ms, plus the external input circuit RC

time constant, an interrupt is generated and a bit is set in the

Status Register. This bit can then be sampled to see if system

power has turned back on. See PIN FUNCTIONS, LINE PIN.

The power-sense circuitry operates by sensing the level of the

voltage presented at the line input pin. This voltage is cen-

tered around VDD and as long as it is either plus or minus a

threshold (about 1V) from VDD a power-sense failure will not

be indicated. With an AC signal present, remaining in this

VDD window longer than a minimum of 2.68ms will activate

the power-sense circuit. The larger the amplitude of the AC

signal, the less time it spends in the VDD window, and the less

likely a power failure will be detected. A 60Hz, 10VP-P sine-

wave voltage is an applicable signal to present at the LINE

input pin to setup the power sense function.

Power Down (See Figure 4)

Power down is a processor-directed operation. A bit is set in

the Interrupt Control Register to initiate operation. 3 pins are

affected. The PSE (Power Supply Enable) output, normally

high, is placed low. The CLK OUT is placed low. The CPUR

output, connected to the processors reset input is also

placed low. In addition, the Serial Interface is disabled.

Power Up (See Figure 5 and Figure 6)

Two conditions will terminate the Power-Down mode. The

first condition (See Figure 5) requires an interrupt. The inter-

rupt can be generated by the alarm circuit, the programma-

ble periodic interrupt signal, or the power sense circuit.

The second condition that releases Power Down occurs

when the level on the VSYS pin rises about 0.7V above the

level at the VBATT input, after previously falling to the level of

VBATT (See Figure 6) in the Battery Backup Mode or VSYS

falls to logic low and returns high in the Single Supply Mode.

8

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