Allen-Bradley InView Marquee 2706-P42, User Manual

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Publication 2706-UM016A-EN-P - June 2002
InView Protocol 9-39
Reading 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 40002-40004 in display address 020.
Transmission:
Figure 9.60 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 40002-40004 having the
decimal contents of 44, 63, and 1 respectively.
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.
Figure 9.61 Response for Requesting Variable Data
Beg of
Frame ADDR FUNC H.O.
ADDR L.O.
ADDR DATA
Number of
register to
read LRC
Error EOF Ready to
rec. resp
: 14 03 00 01 0003 E5 CR LF
Beg of
Frame ADDR FUNC BYTE
COUNT DATA
OUTPUT
REG H.O.
0002 DATA
OUTPUT
REG L.O.
0002 DATA
OUTPUT
REG H.O.
0003 DATA
OUTPUT
REG L.O.
0003
: 14 03 06 00 2C 00 3F
DATA
OUTPUT
REG
H.O.
0004 DATA
OUTPUT
REG L.O.
0004 LRC EOF Ready to
rec. resp
00 01 77 CR LF
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