Rainbow Electronics MAX3107 - Manual (Page 49)

______________________________________________________________________________________ 49
MAX3107
SPI/I
2
C UART with 128-Word FIFOs
and Internal Oscillator
Connector Pin Sharing
The TX and RTS/CLKOUT outputs can be programmed
to be high impedance. This can be used in cases where
the MAX3107 shares a common connector with other
communication devices. Set the output of the MAX3107
to high impedance when the other communication
devices are active. Program MODE1[2]: TxHiZ high to
set TX to a high-impedance state. Program MODE1[3]:
RTSHiZ high to set RTS/CLKOUT to a high-impedance
state. Figure 25 shows an example of connector sharing
with a USB transceiver.
RS-232 5x3 Application
The four GPIOs can be used to implement the other flow-
control signals defined in ITU V.24. Figure 26 shows how
the GPIOs create the DSR, DTR, DCD, and RI signals
found on some RS-232/V.28 interfaces.
Set FlowCtrl[1:0] high to enable automatic hardware
RTS/CTS flow control.
Typical Application Circuit
Figure 27 shows the MAX3107 being used in a half-
duplex RS-485 application. The microcontroller, the
RS-485 transceiver, and the MAX3107 are powered by
3.3V. SPI is used as the controller’s communication inter-
face. The internal oscillator clocks the UART.
The MAX14840 receiver is continually enabled so that
echoing occurs. Enable autoecho suppression in the
MAX3107 UART by setting MODE2[7]: EchoSuprs to 1.
Set MODE1[4]: TranscvCtrl high to enable autotrans-
ceiver direction control to automatically control the DE
input of the transceiver.
Chip Information
PROCESS: BiCMOS
Figure 24. Logic-Level Translation
Figure 25. Connector Sharing with a USB Transceiver
MAX3107
TX
RX
RTS/CLKOUT
AGND DGND
V L V A V EXT
RST
IRQ
SPI/I 2 C
MAX3078
TRANSCEIVER
V CC
DI
DE
RO
V DD
2.5V
1.8V 3.3V
MICROCONTROLLER
MAX3107
TX
RX
MAX13481E
D+
D-
OE
TX/D+
RX/D-
SHARED
CONNECTOR