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OVERVIEW
Model BB-485TBLED converts unbalanced, full-duplex RS-232 signals
to balanced, full or half-duplex RS-422 or RS-485 signals. RS-485 is an
enhanced version of the RS-422 Standard allowing multiple drivers and
receivers on a two-wire or four-wire system.
The RS-232 port, configured as a DCE port, has a female DB25 connector
with pins 2 (TD input), 3 (RD output), and 7 (Signal Ground) supported. Pins
4 (RTS) and 5 (CTS) are tied together, and pins 6 (DSR), 8 (CD), and 20
(DTR) are also tied together. Pins 1 (Frame Ground) and 7 (Signal Ground)
are connected straight through to the RS-485 terminal blocks. The RS-485
terminal blocks support Transmit Data (A-) and (B+), Receive Data (A-) and
(B+), Frame Ground, Signal Ground, and +12 VDC input.
LEDS – TD & RD
Model BB-485TBLED has two LEDs: Transmit Data LED to show when the
RS-485 driver is enabled and Receive Data LED showing data appearing at
pin 3 of the RS-232 port. These are useful for determining if data is getting
through the converter. Note that the TD LED indicates that the RS-485 driver
is enabled. Data must be present on pin 2 of the RS-232 side for data to
be transmitted out of the RS-485 side. If no data is present, no data will be
transmitted even though the TD LED is illuminated.
FLOW CONTROL - JUMPERS
Model BB-485TBLED uses two different methods to enable the RS-485
driver: either by toggling Request to Send (pin 4) of the RS-232 side, or by
automatic sensing of the data on Transmit Data (pin 2) of the RS-232 side.
This option is user-selectable by setting push-on jumpers located next to
the terminal blocks. See Figure 1. Also, by removing both sets of jumpers
completely constantly enables the RS-485 driver and receiver. This makes
the BB-485TBLED act like an RS-422 converter.
BAUD RATE - RESISTOR 9
Resistor R9 is a timing component on the converter, see Figure 1. This
resistor is part of the automatic sensing circuit and affects the baud rate at
which the converter can be used in a two-wire setup. It is factory selected
to run at 9600 baud or higher. With this component, the RS-485 driver will
shut off approximately 1ms after the last character has been sent. If you
need to change the BB-485TBLED to a baud rate other than 9600 baud, you
can change this component. To change the baud rate, remove R9 and add
through-hole component R14, see Table 1. Figures 2 and 3 show how to
interconnect two RS-485 converters using 4-wire and 2-wire methods.
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Category
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Attribute
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Value
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General
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Mounting
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Power
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Serial Type
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Technology
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Temperature
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Features
- Converts RS-232 signals to RS-485 signals
- Extends data communication up to 1219 meters (4000 ft)
- Data rate: up 115.2 k bps
- Quick inline installation
- Terminal block for easy wiring
- Multi-drop capability - up to 32 receivers per driver
- 12 VDC power supply required (not included, sold separately)
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