71M6534 datasheet(74/132 Pages) MAXIM | Exceeds IEC 62053/ANSI C12.20 Standards

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71M6533/G/H and 71M6534/H Data Sheet

FDS_6533_6534_004

Rev 2

Figure 38: Three-Wire EEPROM Connection

4.5 UART0 (TX/RX)

The UART0 RX pin should be pulled down by a 10 kΩ resistor and additionally protected by a 100 pF ceramic

capacitor, as shown in Figure 39.

Figure 39: Connections for UART0

4.6 Optical Interface (UART1)

The OPT_TX and OPT_RX pins can be used for a regular serial interface (by connecting a RS_232

transceiver for example), or they can be used to directly operate optical components (for example, an

infrared diode and phototransistor implementing a FLAG interface). Figure 40 shows the basic connections

for UART1. The OPT_TX pin becomes active when the OPT_TXE[1:0] I/O RAM field is set to 00.

The polarity of the OPT_TX and OPT_RX pins can be inverted with the configuration bits, OPT_TXINV

and OPT_RXINV, respectively.

The OPT_TX output may be modulated at 38 kHz when system power is present. Modulation is not

available in BROWNOUT mode. The OPT_TXMOD bit enables modulation. The duty cycle is controlled

by OPT_FDC[1:0], which can select 50%, 25%, 12.5%, and 6.25% duty cycle. A 6.25% duty cycle means

OPT_TX is low for 6.25% of the period. The OPT_RX pin uses digital signal thresholds and may need an

analog filter when receiving modulated optical signals.

With modulation, an optical emitter can be operated at higher current than nominal, enabling it to

increase the distance along the optical path.

If operation in BROWNOUT mode is desired, the external components should be connected to V3P3D.

71M6533/71M6534

10 kΩ

100 pF

EEPROM

100 kΩ

DIO4

DIO5

CLK

V3P3D

100 kΩ

DIOn

10 kΩ

VCC

71M6533/71M6534

71M6534 Datasheet(PDF) 74 Page - Maxim Integrated Products