Rainbow-electronics DS1680 Manual do Utilizador descarregar pdf (Página 2)

DS1680

2 of 23

Automatic backup and write protection of an external SRAM is provided through the V

CCO

and

CEO pins. The backup energy source used to power the RTC is also used to retain RAM data in the

absence of V

through the V

CCO

pin. The chip-enable output to SRAM, CE0 , is controlled during power

transients to prevent data corruption.

The DS1680’s microprocessor-monitor circuitry provides three basic functions. First, a precision

temperature-compensated reference and comparator circuit monitors the status of V

. When an out-of-

tolerance condition occurs, an internal power-fail signal is generated that forces RST to the active state.

When V

returns to an in-tolerance condition, the RST signal is kept in the active state for t

RPU

to allow

the power supply and processor to stabilize. The DS1680 debounces a pushbutton input and guarantees an

active RST pulse width of t

RST

. The third function is a watchdog timer. The DS1680’s internal timer

forces the RST signal to the active state if the strobe input is not driven low prior to watchdog time-out.

The DS1680 also provides a touch-screen controller along with a 10-bit successive approximation ADC.

The ADC is monotonic (no missing codes) and has an internal analog filter to reduce high frequency

noise.

DS1680 BLOCK DIAGRAM Figure 1

CLOCK

OSC

CLOCK

GEN

PANEL

DRIVE

CONVERT

CONTROL

10-BIT

ADC

INPUT

MUX

TOUCH

DETECT

POWER

CONTROL

RTC

SERIAL

INTERFACE

WATCHDOG

OUTPUT

MUX

BHE

OUT_SELECT

PEN_SELECT

AIN0

AIN1

COEN

CONVERT

PEN_OFF

PD_RST

D0-D7

OSCIN

INT

SCLK

I/O

RST

POWER SWITCH,

WRITE PROTECT,

NV CONTROL,

AND

POWER FAIL

WARNING

BAT

CCO

CEI

CEO

PFI

PFO

ANSELIN

X+

X-

Y+

Y-

NEW_DATA

1 2 3 4 5 6 7 ... 22 23

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