Quickstart Guide
ABB PLC and drives integration using Modbus RTU
Modbus
RTU
‐
7
‐
PLC
and
drives
integration
AC500
and
AC500
eCo
COM
port
overview
AC500
AC500
‐
eCo
CM574
‐
RS
COM1
COM2
COM1
COM2
(optional)
COM1=COM2
(see
COM1
of
AC500,
except
pull
‐
up/pull
‐
down)
COM
Voltage
level
5
V
5
V
3,3
V
3,3
V
5V
Opto
‐
isolated
(electrically
isolated)
YES
YES
NO
optional
*)
NO
YES
Maximum
bus
cable
length
Acc.
to
RS485
standard
Acc.
to
RS485
standard
50
m
*)
Acc
to
RS485
standard
50
m
Acc.
to
RS485
standard
Connection
Terminal
9
pole
D
‐
sub
9
pole
D
‐
sub
*)
Terminal
Terminal
Terminal
Termination
resistor
built
‐
in
NO
NO
NO
NO
NO
Termination
resistor
size
120
Ω
120
Ω
120
Ω
120
Ω
120
Ω
Pull
‐
up/pull
‐
down
resistors
built
‐
in
YES
(connect
with
bridges)
NO
NO
*)
yes
connect
with
bridges
YES
(connect
with
bridges)
YES
(connect
with
bridges)
Pull
‐
up/pull
‐
down
resistor
size
470
Ω
470
Ω
270
Ω
270
Ω
475
Ω
Pull
‐
up/pull
‐
down
resistors
connection
point
Master
(CPU)
COM
port
Master
(CPU)
COM
port
Master
(CPU)
COM
port
Master
(CPU)
COM
port
Master
(CPU)
COM
port
Pull
‐
up/pull
‐
down
connection
Bridges:
1
to
2
and
3
to
4
External
470
Ω
resistors
External
270
Ω
resistors
Bridges:
1
to
2
and
3
to
4
Bridges:
1
to
2
and
3
to
4
*)
using
TK506
RS485
isolator
for
PM554
/
PM564
with
index
A3
and
higher
Drives
with
embedded
fieldbus
The
following
ABB
drives
have
Modbus
RTU
embedded:
ACS310
ACS/ACH550
ACS850
Since
the
built
‐
in
end
termination
of
the
drive
automatically
also
activates
pull
‐
up/pull
‐
down
resistors,
it
is
recommended
to
skip
the
built
‐
in
option.
It
is
recommended
to
connect
a
separate
end
termination
resistor
to
the
first
node
(i.e.
the
PLC
COM
interface)
and
the
last
node
(i.e.
the
last
drive
on
the
bus).
For
connection
examples,
see
chapter
“Installation
examples”.
