12
Keystone
OM9 - EPI2 PrOfIbus DPV1 IntErfacE
InstallatIon & MaIntenance InstructIons
6.3 profibus/hardwired mode selection
the EPI
2
DPV1 interface manages the Profibus/
hardwired mode selection by means of the
input indicated with HW MODE. the physical
input accepts any voltage from 24 to 125V Dc or
ac, polarity insensitive.
When no voltage is applied, the actuator is
Profibus controlled and it is possible to send
commands and read the status by Profibus DP.
When an appropriate voltage is applied to
the HW MODE input, the actuator runs under
hardwired control. In this condition the Profibus
master can only read the actuator status, while
the actuator follows the hardwired Open and
close controls connected to the terminal board.
for further details see the relevant wiring
diagram and the user manual:
EPI
2
Quarter-turn Electric actuator IOM.
7 profibus dp description
Profibus is a vendor-independent, open
fieldbus standard used in a wide range of
applications in process automation. Vendor
independence and openness are ensured by
the international standards En 50170 and
En 50254. the DP communication profile is
designed for data exchange at the field level.
the central controllers (i.e. PLc) communicate
via a serial connection with field devices (as
sensors and actuators). Data exchange is
mainly cyclic. the central controller (called
master) cyclically reads the input information
from the field devices (called slaves) and
cyclically writes the output information to the
slaves. In addition the Profibus DP provides
communication services for parameterization,
alarm handling, and monitoring of intelligent
Logical token passing between master devices
PLc
Pc
General
Drive
transmitter
EPI
2
actuators
slave devices
Master devices
DP master class 1 (DPM 1):
this is the central controller that cyclically
exchanges information with the field
devices. typical devices are PLc, Dcs or Pc.
DP master class 2 (DPM 2):
these devices are necessary for
commissioning, maintenance and
diagnostics.
slave:
field device, i.e. transmitters, actuators,
drives, etc.
the figure below shows a Profibus DP
configuration with two master devices and
different slave devices.
field devices. the maximum number of
master and slave devices in a bus segment
is 32 without repeaters. With repeaters the
number can be extended to 126 on one bus.
the maximum cable length depends on the
speed of transmission. the higher the speed,
the shorter is the length. for instance, with
baud rate 93.75 Kb/sec, the max cable length
is 1,200 m without repeaters and 10,000 m with
repeaters.
Mono-master or multi-master system
configuration can be provided. bus access
is controlled by a token passing procedure
between masters and polling (master-slave
procedure) between master and slaves.
