11. Mo
11.1.
Modbus is a
Slaves
.
Slave device
Master. Slave
for sending c
bus at any on
Modbus is m
on the same
Each Slave d
Master sends
11.2.
Modbus Slav
The register t
Register N
Discrete In
Coil
Input Reg
Holding Re
11.3.
For commun
connection d
Caution:
The RS-485
shield should
Caution:
RS-485 has p
and all ‘GND
Caution:
The RS-485
odbus RT
Modb
master-slave
s simply wait
es do not have
commands to s
ne time, but up
ost commonly
bus.
device must ha
s will contain t
Modb
ve devices sto
types are sum
Name
R
nput
D
ister
A
gister An
Modb
ication over R
iagrams below
cable must be
d be connected
polarised data
’s are connec
cable must be
TU
us backgr
protocol, whic
until they rece
e the ability to
slave devices
p to 247 slave
y used over RS
ave a unique
this Slave ID a
us registe
re data in regi
mmarised belo
Register Type
Digital Input
Digital Output
Analogue Inpu
nalogue Outpu
us connec
RS-485 all 3 co
w.
e a shielded d
d to GND at o
a connections.
ted together.
e daisy-chaine
round
ch means ther
eive a comman
o send comma
and receiving
es can be conn
S-485, which
ID on the bus,
and only the S
ers
isters. There a
w:
e
Read on
a value
Read an
t
Read on
value (0
ut
Read an
which h
ctions
onnections are
ata cable. Ma
one end only.
. It is crucial th
ed in a bus net
re are two type
nd from a Mas
ands to other d
g data. Modbu
nected at a tim
is a hardware
, which is refe
Slave with that
are four regist
nly register us
of 0 or 1.
nd write acces
nly register us
0-65535)
nd write acces
holds a 16-bit v
e needed. The
ins flex or oth
hat all ‘A’s are
twork. T-junct
es of Modbus
ster, act upon
devices on the
s only permits
me.
standard allo
erred to as a
S
t Slave ID will
er types and e
Descrip
sed for holding
ssible register
sed for status
ssible register
value (0-6553
ese are labele
er unshielded
e connected to
ions (e.g. star
device, Modb
that comman
e bus. Master
s there to be o
wing multiple
Slave ID
. Each
reply.
each type has
ption
g status inform
r which holds a
information wh
r used for statu
5)
ed A, B and G
cable should
gether, all ‘B’s
r network wirin
bus
Masters
an
nd and send a
devices are re
one Master de
devices to be
h Modbus com
s its own regist
mation which h
a value of 0 or
which holds a 1
us information
ND. Please r
not be used.
s are connecte
ng) are not per
Page 34
nd Modbus
reply to the
esponsible
vice on the
e connected
mmand the
ter bank.
holds
r 1.
6-bit
n
efer to the
The cable
ed together
rmitted.
All manuals and user guides at all-guides.com
