71M6541DSLASHFSLASHG datasheet(101/166 Pages) MAXIM

101 / 166 page

71M6541D/F/G and 71M6542F/G Data Sheet

Rev 5

101

4.9

Connecting Three-Wire EEPROMs

µWire EEPROMs and other compatible devices should be connected to the DIO pins SEGDIO2/SDCK

and SEGDIO3/SDATA, as described in 2.5.9 EEPROM Interface.

4.10

UART0 (TX/RX)

The UART0 RX pin should be pulled down by a 10 k

Ω resistor and additionally protected by a 100 pF

ceramic capacitor, as shown in Figure 40.

Figure 40: Connections for UART0

4.11

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 41 shows the basic connections for

UART1. The OPT_TX pin becomes active when the I/O RAM control field OPT_TXE (I/O RAM 0x2456[3:2])

is set to 01.

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

(I/O RAM 0x2456[0]) and OPT_RXINV (I/O RAM 0x2457[1]), respectively.

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

available in BRN mode. The OPT_TXMOD bit (I/O RAM 0x2456[1]) enables modulation. The duty cycle is

controlled by OPT_FDC[1:0] (I/O RAM 0x2457[5:4]), 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. It 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 BRN mode is desired, the external components should be connected to V3P3D. However,

it is recommended to limit the current to a few mA.

71M654x

10 k

100 pF

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