Mode of transmission – Rockwell Automation 2706-P42_P43_P44_P72_P74_P92_P94 InView Marquee Message Display User Manual User Manual

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Publication 2706-UM016D-EN-P - March 2006

4-12 InView Protocol

The following table shows the format of the 01 Frame used for the
downloading of messages to the displays.

Function 01 Used for Downloading of Messages

Messages are downloaded to all displays on the Modbus ASCII display
network. A broadcast address is used that requires no response from
the displays. Modbus ASCII protocol uses address 00h for
broadcasting information from one device to the next. This is
generally reserved for PLC to PLC communications. For this reason,
address 255 (0xff) is used.

Mode of Transmission

Mode of transmission is the format in which messages are transmitted
over the network. Characteristics of the Modbus ASCII system are:

Coding Systems - hexadecimal (uses ASCII printable characters:
0-9, A-F).

Modbus allows the format for data transmission.

• Communication rate: user selectable
• Format: Number of bits per character - 1 start bit, 7 data, 1

(optional) parity bit, 1 or 2 stop bits.

For the products, the data communication rate and format shall be
9600 baud (maximum), 1 start bit, 7 data bits, even parity, 2 stop bits.

InView Display Memory Map

Information transmitted to the displays writes or reads information
into holding registers. The holding registers used in the products are
40001 to 40167. Holding registers 40001 to 40103 can be written to.
Registers 40001 to 40100, and 40103 to 40167 can be read from.

The product has three basic areas for registers, 100 registers for
variables, 3 registers for message control, and 64 registers for the
message queue. When referencing a holding register, Modbus ASCII
requires that 40001 be subtracted from the holding register address.

Beginning of
Frame

Address

Function

Starting
Register Lo

Starting
Register Hi

Data

Error Check EOF

Ready to
rec. resp

2-char 16
bits

InView
Protocol

2-char 16
bits