©
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tion
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10
-S
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2020
EVO/
™ECM-Modbus RTU
Series 2
Page 6
Application Guide
©2020 All Rights Reserved
Evolution Controls Inc.
San Diego, CA USA
Traditionally, a Modbus trunk requires a pair of external resistors to pull up and pull down the two
trunk wires to maintain the trunk at a known biasing voltage when no device is communicating.
The EVO/ECM-Modbus is equipped with internal failsafe biasing so no external biasing is required.
EVO
™
/ECM-Modbus communications is half-duplex. All devices contain a transmitter and a
receiver. Only one transmitter on a trunk can be transmitting at a time. All other devices on
the trunk (Master and RTU slaves) must be in receive. When a Master finishes sending, it must
quickly "turn-around" so it is ready to receive a reply from the RTU.
The EVO
™
/ECM-Modbus reply is very fast. Some Masters, especially those where turn-around is
controlled over a higher-level network (server architecture) cannot turn around fast enough to
receive the RTU's reply. The Reply Delay flag in register 14 can be set to delay the RTU's reply.
MOTOR CONNECTION
PWM Motor Output
A four-conductor cable connects each motor to
the EVO/ECM-Modbus RTU output connector.
Plug the motor end of the cable into the motor
and plug the circuit board end into motor
connection 1, 2, 3, or 4 on the RTU.
The motor control cable may be up to 150 meters
(5
00’) long.
Motor cables are prefabricated, with an
ECM Motor connector on one end, and a
small 4-pin circuit board connector on the
other.
Order
Motor Cable
ECM
-
CBL_ _
Custom Lengths
substitute the length in feet
for
the last two digits.
Order connectors from
Digikey PN ED1702-ND
http://www.digikey.com
Commu
nications
Moto
r
4
Motor
3
Motor
2
Motor
1
