DS1344D-33+【PDF 10/20 页】IC RTC SPI 3.3V 14TDFN-EP

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Maxim Integrated

Low-Current SPI/3-Wire RTCs

DS1343/DS1344

Reading and Writing in Burst Mode

Burst mode is similar to a single-byte read or write,

except that CE is kept high and additional SCLK cycles

are sent until the end of the burst. The clock registers

and the user RAM can be read or written in burst mode.

The address pointer wraps around to 00h after reaching

1Fh (RTC), and the address pointer wraps around to 20h

after reaching 7Fh (RAM). See Figure 6.

3-Wire Interface

The 3-wire interface mode operates similarly to the SPI

mode. However, in 3-wire mode there is one I/O instead

of separate data-in and data-out signals. The 3-wire

interface consists of the I/O (SDI and SDO pins con-

nected together), CE, and SCLK pins. In 3-wire mode,

each byte is shifted in LSB first, unlike SPI mode, where

each byte is shifted in MSB first.

As is the case with the SPI mode, an address byte is

written to the device followed by a single data byte or

multiple data bytes. Figure 7 illustrates a write cycle, and

Figure 8 illustrates a read cycle. In 3-wire mode, data is

input on the rising edge of SCLK and output on the falling

edge of SCLK.

Applications Information

Power-Supply Decoupling

To achieve the best results when using the devices,

decouple the VCC power supply with a 0.01F and/or

0.1F capacitor. Use a high-quality, ceramic, surface-

mount capacitor if possible. Surface-mount components

minimize lead inductance, which improves performance,

and ceramic capacitors tend to have adequate high-

frequency response for decoupling applications.

Using Open-Drain Outputs

The INT0 and INT1 outputs are open drain and therefore

require external pullup resistors to realize a logic-high

output level.

Battery Charge Protection

The devices contain Maxim’s redundant battery-charge

protection circuit to prevent any charging of an external

battery. The DS1343 and DS1344 are recognized by

Underwriters Laboratories (UL) under file E141114.

Figure 7. 3-Wire Single-Byte Write

Figure 8. 3-Wire Single-Byte Read

SCLK

I/O*

*I/O IS SDI AND SDO CONNECTED TOGETHER.

SERMODE = GND.

HIGH-Z

R/W

SCLK

HIGH-Z

*I/O IS SDI AND SDO CONNECTED TOGETHER.

SERMODE = GND

I/O*

R/W

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