Rainbow Electronics 71M6542G - Manual (Page 101)

v1.1 © 2008–2011 Teridian Semiconductor Corporation 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 00.
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.
TX
RX
71M654x
10 k
Ω
100 pF
RX
TX