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A1000 & A2000 USERS MANUAL 8
BAUD RATE
The A1000 and A2000 series converters each contain a 10-position DIP
switch located on the rear panel. The DIP switch is used to select the
correct communications baud rate and must be set to the same value as
the devices connected to the RS-485 OUT connector. Only one baud
rate switch may be turned on at one time.
L E D S
The A1000 contains three status LEDs labelled FAULT, POWER and
TRANSMIT located on the converter front panel. The A2000 contains
two status LEDs labelled PWR and TX located on the converter rear
panel. The status indicators are useful while troubleshooting suspected
system faults and provide visual status indication during normal system
operation.
The A2000 converter LEDs may be disabled internally. Low power
applications, typically powered by batteries or solar panels, can benefit
significantly by disabling the status LEDs.
The
A2000
power
consumption may be reduced by up to 50% with the LEDs disabled. To
disable the status LEDs, remove the A2000 top cover and locate the 3-
pin strip on the PC board directly behind the LEDs. Lift the jumper bar
from the pin strip and place it over the two pins located closest to 'LEDS
OFF' written on the PC board.
The POWER (A1000) and PWR (A2000) LEDs are pilot lights that
indicate adequate power supply voltage is applied to the converter.
The TRANSMIT (A1000) and TX (A2000) LEDs illuminate as data is
transmitted from a host computer onto the RS-485 communications bus.
The illumination intensity will vary and may become hard to detect as the
baud rate increases.
The A1000 FAULT LED will illuminate if excessive current is being drawn
from the internal +24Vdc one amp power supply.
RS-485 TERMINATIONS
The proper termination techniques for any RS-485 system require two
biasing resistors and two termination resistors. There must be one pull-up
resistor between the DATA+ line and +5Vdc on each RS-485 network.
There should also be a pull-down resistor from the DATA- line to ground.
These two resistors are the biasing resistors and are normally positioned
at the HOST end of the cable. The RS-485 standard also requires two
resistors across the data lines for proper termination. Two 220 Ω resistors
should be placed across the data lines DATA+ and DATA-. The resistors
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