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dc2364af
DEMO MANUAL DC2364A
Quick start proceDure
OVERVIEW
The LTC2873 multiprotocol transceiver comprises one
RS485 driver and receiver and one RS232 driver and
receiver. A two-pin bus interface is shared with the RS485
and RS232 transceivers and only one can be active at a
given time. The LTC2873 requires a Main Supply, VCC
(3Vto5.5V) and a Logic Supply, VL(1.7V to 5.5V).
The DC2364A is designed to be used stand-alone or
interface directly with a Linduino microcontroller board
(DC2026) in a shield configuration. It is equally compatible
with Arduino, although Linduino is preferred because it
adds a fully isolated USB port, offering added protection
to the connecting computer. A Linduino sketch is provided
that, when loaded and run, displays a menu of options for
controlling and using the DC2364A. This sketch can be
customized as needed.
The DC2364A provides a means to control and observe
nearly every pin on the LTC2873. The control pins can be
driven externally, set high or low with a jumper, or con-
trolled with a Linduino microcontroller (when attached).
Level shifting buffers are included on the DC2364A so
that the Linduino can control the signals to the LTC2873,
yet support and preserve the full range of VLvoltages
and logic levels applied to the LTC2873 from 1.7V to VCC.
More Features of the DC2364A:
n Turrets for supply connections are on the right edge
of the board. These connections are optional if used
with a Linduino.
n Test points and terminal block connections for bus
pins on are on the right edge of the board.
n Test points and jumpers for logic-level signals are on
the left edge of the board.
n A Green LED indicates the presence of a low on Data
Input, DI.
n A Yellow LED indicates the presence of a low on
Receiver Output, RO.
n 100k pull-up or pull-down resistors on all logic I/O
pins provide a defined logic state in the absence of a
driving signal or jumper.
n Four switches near the bottom left of the board can
be used to give the board a unique address acces-
sible by the Linduino, allowing the code to support
multiple boards, uniquely addressed.
LTC2873 OPERATION
The LTC2873 enables a single channel RS232 driver and
RS232 receiver or one RS485 driver and one RS485 re-
ceiver, selectable with the 485/232 control pin.
In RS232 mode (485/232 low), the driver and receiver
are always active and DE485/F232 enables fast mode for
up to 1Mbps.
In RS485 mode (485/232 high), the driver and receiver
are only active if their associated enable pins (DE485/
F232 and RE485) are driven high and low, respectively.
RS485 termination can be switched in by setting the
TE485 pin low. This enables a 120Ω resistor between
A/DO and B/RI.
JUMPERS
Logic Level Jumpers:
Logic interface pins (LB, TE485, 485/232, RE485, DE485/
F232, DI, SHDN) all have jumpers that can be set in three
positions to control the pin state: “GND,” “VL”and “ENuC.”
“GND” and “VL”are used to set the state of the pin low or
high. “ENuC” enables Linduino control of the pin.
To drive the signal from an external source, set the jumper
for that pin to the GND position. This connects a 50Ω
termination resistor from the pin to ground that can be
overdriven with an external source connected to the test
point on the left side of the board. Alternately, the jumper
can be removed entirely if the 50Ω load is undesirable.
Supply Jumpers:
There are two jumpers that control the Logic Supply
(VL) and Main Supply (VCC) to the LTC2873. For each,
the “3V3” or “5V” settings connects the Linduino 3.3V
or 5V regulated supply to those pins. With the jumper
in the “EXT” position, VCC and VLwill be routed to the
LTC2873 from the turrets on the right edge of the board.
If the DC2364A is used without the Linduino, the “EXT”
setting must be used.
