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LEDs on main circuit board
The WEB-645-AX's main circuit board has LEDs for LON and
Serial ports (see Fig. 2. on page 6 for location):
LON
Two LEDs are located near the LON port and show transmit
and receive activity.
• The yellow transmit LED (TxD) indicates that the WEB
Controller is transmitting a message on the LON trunk.
• The green receive LED (RxD) indicates that another
LonWorks device is transmitting a message.
Serial
Two LEDs for each RS-232 and RS-485 serial port are located
near the ports on the main circuit board. They show transmit
and receive activity for these serial ports.
• The yellow transmit LED indicates that the controller is
sending data out the serial port over a communications line
to a connected device.
• The green receive LED indicates that the WEBs-AX is
receiving data from a device.
These LEDs are driven by pulse detectors that provide a fixed
on-time when data is detected on the port. If the receive LED
is on constantly, this indicates a problem with the
communications channel, such as a shorted wire or reversed
wiring.
CONTROLLER JUMPERS
The controller has jumper blocks to allow for Serial Shell mode
operation and for RS-485 port biasing, as described below.
Serial Shell mode
The controller's NPM6E processor module has a four-pin
jumper header and a 2-pin jumper block that you can
reposition, as needed, to enable or disable "Serial Shell"
mode operation. In this mode, the RS-232 COM1 port on the
controller allows "system shell" menu access, using serial
parameters: 115200, 8, N, 1.
NOTE: You must reboot the controller after reposition-
ing this jumper before any serial shell mode
change becomes effective. When done, don't for-
get to return to the jumper block to its normal
position and reboot again.
The default jumper setting is "Normal" (no serial shell), see
"WEB-645-AX board layout details.," page 6.
WEB-645, CP-645 NETWORK CONTROLLER
RS-485 port biasing
The controller has four RS-485 ports (COM3, COM4, COM5,
and COM6) on the bottom of the circuit board. Each RS-485
port has an associated four-pin "TERMn" header for jumpers.
See RS-485 bias jumpers on WEB-645-AX..
COM3
COM4
Fig. 4. RS-485 bias jumpers on WEB-645-AX.
On any RS-485 port's "TERM" header, you can install two 2-
pin jumper blocks to enable "RS-485 biasing", if needed. See
RS-485 bias jumpers on WEB-645-AX.
As shipped from the factory, these pins are not shorted, thus
each RS-485 port is unbiased. See "A full discussion of
communications line termination is beyond the scope of this
document." for related background details.
NOTE: A full discussion of communications line termi-
nation is beyond the scope of this document.
Need for RS-485 bias
Biasing sometimes improves RS-485 communications by
eliminating "indeterminate" idle states. When you install two,
2-pin shorting blocks on an RS-485 port's bias jumper pins,
this adds two onboard 3.3K ohm resistors into the controller's
RS-485 circuit, as follows:
• from RS-485 "+" to 5V.
• from RS-485 "-" to Ground.
NOTE: From RS-485 "-" to Ground.In general, only one
device on an RS-485 trunk should be biased. Oth-
erwise, undue circuit loading may result, with
fewer devices supported.
NOTE: RS-485 bias resistors are different than "termina-
tion resistors", externally installed at the two
physical ends of a daisy-chained RS-485 trunk,
across the "+" and "-" terminals. Termination
resistors are typically 100 or 120 ohm value
resistors.
NOTE: Whenever termination resistors are used, RS-485
biasing is typically required.
11
COM5
COM6
62-0432—01
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