Red Lion LEGEND - Manual (Page 45)

COMMUNICATION FORMAT
The half-duplex communication operation sends data by switching voltage
levels on the common pair of wires. Data is received by monitoring the levels
and interpreting the codes that were transmitted. After the Legend Plus
receives a Transmit Command or Print Request, it waits the Serial Transmit
Delay time before it begins transmitting data. The serial transmit delay can be
programmed for 0.002 or 0.100 second. For data to be interpreted correctly,
there must be identical formats and baud rates between the communicating
devices. The formats available for the Legend Plus unit are 1 start bit, 7 or 8
data bits, No parity or 1 parity bit (odd or even) and 1 stop bit. The available
baud rates are; 1200, 2400, 4800, or 9600 baud. If any extended characters are
to be used or transmitted, the Legend Plus communication port should be
set-up for Parity of “NONE-8B”. This configures the unit to accept and
transmit 8 data bits with no parity.
Before serial communication can take place, the unit must be programmed
to the same baud rate and parity as the connected equipment. In addition, the
loop address number and print options should be known. When used with a
terminal or host computer and only one unit is employed, an address of zero
(00) may be used to eliminate the requirement for the address command when
sending a command. If more than one unit is on the line, assignment of unique
non-zero addresses is required.
SENDING COMMANDS AND DATA
When sending commands to the Legend Plus unit, a command string must
be constructed. The command string may consist of command codes, value
identifiers, and numerical data. Below is a list of commands and value
identifiers that are used when communicating with the LGPM unit.
COMMAND DESCRIPTION
M (4DH) Request message command; Followed by the message
number 0 to 9.
MC (4DH, 43H) Clear message command.
N (4EH) Address command; Followed by the address number 1
to 99.
P (50H) Transmit print options command; Transmits the options
selected in the Program Options Module section.
R (52H) Reset value command; Followed by one Value
Identifier (E, I, J, O, or 1 to 6 [for outputs]).
T (54H) Transmit value command; Followed by one Value
Identifier (A-O).
V (56H) Change value command; Followed by one Value
Identifier (A-E, K-O), then the proper numerical data.
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DATA FORMAT
10 BIT FRAME
[Parity = ODD-7B, EVEN-7B]
DATA FORMAT
10 BIT FRAME
[Parity = NONE-8B]