Red Lion LEGEND - Manual (Page 51)

TROUBLESHOOTING SERIAL COMMUNICATIONS
If problems are encountered when interfacing the Legend Plus(s) and host
devices or printers, the following check list can be used to help find a solution.
1. Check all wiring. Refer to the previous application examples and use them as a
guide to check your serial communication wiring. Proper polarity of all
Legend Plus(s) and other peripherals must be observed.
2. Check RS232/RS485 configuration jumpers for proper interface selection.
3. If the Legend Plus is connected to a “host computer”, device or printer, check
to make sure that the computer or device is configured with the same
communication format as the Legend Plus. The communication format that
the Legend Plus will accept is; 1 start bit, 7 or 8 data bits, no parity or 1 parity
bit (odd or even), and 1 stop bit.
4. Check the baud rate and parity in the Program Communication Module and
make sure all devices on the line have the same baud rate and parity.
5. Check the Legend Plus’s unit address. If the Address command is not used
when transmitting a command to the Legend Plus, the Legend Plus’s address
must be set to 0. See “Sending Commands & Data” for command structure.
6. If two-way communications are to be established between the Legend Plus and
a computer, have the computer receive transmissions from the Legend Plus
first. Activating a User Input, programmed for the print request function, will
initiate transmissions from the Legend Plus.
7. When sending commands to the Legend Plus, an asterisk *(2Ah) must
terminate the command. NO CARRIAGE RETURNS (0Dh) OR LINE FEED
(0Ah) CHARACTERS SHOULD BE SENT TO THE LEGEND PLUS. If
they are sent, the Legend Plus will respond by transmitting an “E”.
8. In multiple unit configurations, make sure each unit has a different address
other than zero. If a transmit value or print request command is issued, an
asterisk (
S ) must be sent before sending another transmission.
9. In some RS485 applications, a twisted pair with a signal ground may be needed
to establish a ground reference. The signal ground is required if the equipment
does not have internal bias resistors connected to the transceiver lines. The
signal ground is connected from only one Legend Plus to the equipment.
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