Linear Technology DC1786A Demo Manual

DESCRIPTION
Demonstration circuit 1786A showcases the LTC2871
RS232/RS485 multiprotocol transceiver with integrated
termination. Separate supply inputs power the interface
and logic sections, permitting operation of the logic con-
trol and I/O down to 1.7V. LEDs indicate when supplies
are present. All control pins are accessible via a turret
for external connections, or they may be set by jumpers.
All logic I/O and interface I/O lines are routed to turrets.
The RS485 interface lines are also available at a terminal
QUICK START PROCEDURE
The LTC2871 multiprotocol transceiver contains two RS232
drivers, two RS232 receivers, one RS485 driver and one
RS485 receiver. All drivers and receivers may be accessed
independently and simultaneously. The LTC2871 also in-
cludes on-chip supply generation for RS232, permitting
operation from a single 3V to 5.5V V
logic I/O supply pin (V ) permits the LTC2871 to adapt to
L
any logic level ranging from 1.7V up to V
The LTC2871 also includes selectable RS485 termina-
tions, as well as switching for half- and full-duplex modes,
eliminating the need for external jumpers or relays for
configuration in different modes.
DC1786A Includes:
• Bananas and turrets for supply connections along
the upper edge of the board
RS232/RS485 Multiprotocol Transceiver
with Integrated Termination
block for convenient connection of a transmission line.
Because the LTC2871 contains half-/full-duplex switching
control it is unnecessary to jumper A and B to Y and Z for
half-duplex operation.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, μModule, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
supply. A separate
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DEMO MANUAL DC1786A
• Turrets for logic I/O along the left edge of the board
• Turrets for RS232 and RS485 interface connections
along the right edge of the board
• A terminal block, J5, for RS485 connections
• Turrets and jumpers for selecting modes along bot-
tom edge of board. There are no pull-up or pull-down
resistors on the control lines; known states must be
asserted by jumpers or by applying a definitive logic
level to the turrets.
• Green LEDs to indicated the presence of V
V . Note that the V LED, D1, unavoidably dims and
L L
extinguishes at V <2V.
L
• 10k pull-up resistors on DI, DIN1 and DIN2 to assert
a known logic-1 state when these turrets are left open
LTC2871IUHF
and
CC
dc1786af
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