Red Lion LEGEND - Manual (Page 52)

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 (*) 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 shave 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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