Rockwell Automation 2706-P42_P43_P44_P72_P74_P92_P94 InView Marquee Message Display User Manual User Manual

Page 105

Publication 2706-UM016D-EN-P - March 2006

InView Protocol 4-39

The normal response to a function 03 query is to echo the address,
function code, starting address and the data for the registers that were
requested.

Response for Requesting Message Queue Data

Read Variables in a Display using a Modbus ASCII 03 frame

This function allows the ability to read variable data stored in a
display. A maximum of 100 registers can be read since there is a
maximum of 100 registers of data. Below is an example of the request
for registers 40002 through 40004 in display address 020.

Transmission:

Query for Requesting Variable Data

Response:

The addressed slave responds with its address and the function code,
followed by the information field. The information field contains 2
bytes describing the quantity of data bytes to be returned. The
contents of the registers requested (DATA) are two bytes each, with
the binary content right justified within each pair of characters. Below
shows the response to query for registers 40002 through 40004 having
the decimal contents of 44, 63, and 1 respectively.

Beginning
of Frame

ADDR

FUNC

BYTE
COUNT

DATA
OUTPUT
REG H.O.
0066

DATA
OUTPUT
REG L.O.
0066

DATA
OUTPUT
REG H.O.
0067

DATA
OUTPUT
REG L.O.
0067

DATA
OUTPUT
REG H.O.
0068

DATA
OUTPUT
REG L.O.
0068

LRC

EOF

Ready to
rec. resp

Beginning
of Frame

ADDR

FUNC

H.O.
ADDR

L.O.
ADDR

DATA Number
of register to
read

LRC
Error

EOF

Ready to
rec. resp

0003