Parameter
structure
Keypad
and
display
Parameter
x.00
Parameter
description
protocol
Performance
decremented
on
the
master
device
before
passing
to
the
protocol.
The
register
file
type
code
is
NOT
transmitted
by
MODBUS
and
all
this
behavior
is
that
#0.0
cannot
be
accessed.
The
following
function
codes
are
supported:
Table
6-1
Master
request
Table
6-2
Slave
response
FC06
Write
single
register
Table
6-3
Master
request
Data
types
format
Advanced
parameter
descriptions
Serial
comms
6.2.2
Slave
address
The
first
byte
of
the
frame
is
the
slave
node
address.
Valid
slave
node
addresses
are
1
through
247
decimal.
In
the
master
request
this
byte
indicates
the
target
slave
node;
in
the
slave
response
this
byte
indicates
the
address
of
the
slave
sending
the
response.
Global
addressing
Address
zero
addresses
all
slave
nodes
on
the
network.
Slave
nodes
suppress
the
response
messages
for
broadcast
requests.
6.2.3
MODBUS
registers
The
MODBUS
register
address
range
is
16bit
(65536
registers)
which
at
the
protocol
level
is
represented
by
indexes
0
through
65535.
PLC
registers
Modicon
PLCs
typically
define
4
register
'files'
each
containing
65536
registers.
Traditionally,
the
registers
are
referenced
1
through
65536
rather
than
0
through
65535.
The
register
address
is
therefore
register
files
can
be
considered
to
map
onto
a
single
register
address
space.
However,
specific
function
codes
are
defined
in
MODBUS
to
support
access
to
the
"coil"
registers.
All
standard
CT
drive
parameters
are
mapped
to
register
file
'4'
and
the
coil
function
codes
are
not
required.
CT
parameter
mapping
All
CT
products
are
parameterized
using
the
#menu.param
notation.
Indexes
'menu'
and
'param'
are
in
the
range
0
through
99.
The
#menu.param
is
mapped
into
the
MODBUS
register
space
as
menu*100
+
param.
To
correctly
map
the
parameters
at
the
application
layer,
the
slave
device
increments
the
received
register
address.
The
consequence
of
6.2.6
Function
codes
The
function
code
determines
the
context
and
format
of
the
message
data.
Bit
7
of
the
function
code
is
used
in
the
slave
response
to
indicate
an
exception.
FC03
Read
multiple
Read
a
contiguous
array
of
registers.
The
slave
imposes
an
upper
limit
on
the
number
of
registers,
which
can
be
read.
If
this
is
exceeded
the
slave
will
issue
an
exception
code
2.
Writes
a
value
to
a
single
16bit
register.
The
normal
response
is
an
echo
of
the
request,
returned
after
the
register
contents
have
been
written.
The
register
address
can
correspond
to
a
32bit
parameter
but
only
16
bits
of
data
can
be
sent.
The
MODBUS
protocol
specification
defines
registers
as
16bit
signed
integers.
All
CT
devices
support
this
data
size.
Refer
to
the
section
6.2.7
Extended
data
types
on
page
208
for
detail
on
accessing
32bit
register
data.
6.2.4
Data
consistency
All
CT
devices
support
a
minimum
data
consistency
of
one
parameter
(16bit
or
32bit
data).
Some
devices
support
consistency
for
a
complete
multiple
register
transaction.
6.2.5
Data
encoding
MODBUS
RTU
uses
a
'big-endian'
representation
for
addresses
and
data
items
(except
the
CRC,
which
is
'little-endian').
This
means
that
when
a
numerical
quantity
larger
than
a
single
byte
is
transmitted,
the
MOST
significant
byte
is
sent
first.
So
for
example
16
-
bits
0x1234
would
be
0x12
0x34
32
-
bits
0x12345678
would
be
0x12
0x34
0x56
0x78
Mentor
MP
Advanced
User
Guide
207
Issue
Number:
4
www.onxcontrol.com
Byte
Description
0
Slave
destination
node
address
1
through
247,
0
is
global
1
Function
code
0x03
2
Start
register
address
MSB
3
Start
register
address
LSB
4
Number
of
16bit
registers
MSB
5
Number
of
16bit
registers
LSB
6
CRC
LSB
7
CRC
MSB
Byte
Description
0
Slave
node
address
1
through
247
0
is
global
1
Function
code
0x06
2
Register
address
MSB
3
Register
address
LSB
4
Register
data
MSB
5
Register
data
LSB
6
CRC
LSB
7
CRC
MSB
CT
parameter
MODBUS
PLC
register
Register
address
(protocol
level)
Comments
#X.Y
40000
+
X
x
100
+
Y
X
x
100
+
Y
-
1
#0.0
cannot
be
accessed
Examples:
#1.2
40102
101
#1.0
40100
99
#0.1
40001
0
#70.0
47000
6999
Byte
Description
0
Slave
source
node
address
1
Function
code
0x03
2
Length
of
register
data
in
read
block
(in
bytes)
3
Register
data
0
MSB
4
Register
data
0
LSB
3+byte
count
CRC
LSB
4+byte
count
CRC
MSB
Code
Description
3
Read
multiple
16bit
registers
6
Write
single
register
16
Write
multiple
16bit
registers
23
Read
and
write
multiple
16bit
registers
File
type
Description
1
Read
only
bits
("coil")
2
Read
/
write
bits
("coil")
3
Read
only
16bit
register
4
Read
/
write
16bit
register