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EVO/
™ECM-Modbus RTU
Series 2
Page 10
Application Guide
©2020 All Rights Reserved
Evolution Controls Inc.
San Diego, CA USA
REGISTER ASSIGNMENTS
Register 1 - On/Off Control and Status
Low Byte
Motor Enable/Disable Nibble
Each of the 4 bits in this nibble represents the associated motor enable command. If the
associated bit is set (1), and the associated flow index is greater than "0" the motor runs. If the
bit is clear (0), the motor stops regardless of the associated flow index. The Modbus RTU Master
writes to this nibble to enable/disable motors and reads the nibble to retrieve the motor
enable/disable status.
Bit 0 = Motor 1, Bit 1 = Motor 2, Bit 2 = Motor 3, and Bit 3 = Motor 4.
RPM Alarm Nibble
Each of the 4 bits in this nibble represents the associated motor alarm status. If the associated bit
is set (1), the motor RPM is not between the low and high RPM limits. If the associated bit is clear
(0), the associated motor RPM is between the low and high RPM limits. When a motor is turned
off, the RPM Alarm bit is cleared. The alarm bit is held clear for 20 seconds after a starting a
motor. When an RPM alarm bit is set, the alarm clears when the associated motor RPM is at least
50 RPM or 100 RPM inside the low and high RPM limits depending on the hysteresis selection bit
(Coil 29) in Register 14.
Bit 4 = Motor 1, Bit 5 = Motor 2, Bit 6 = Motor 3, and Bit 7 = Motor 4.
High Byte
External Command Flag
A Modbus RTU Master may use the EC flag to mark that it has read default values from the
EVO/ECM-Modbus RTU. The EC flag is cleared if a configuration tool or global command changes
default values. Resetting the RTU also clears the EC flag.
Use of this flag is optional. Using the EC flag increases communications throughput. If the EC flag
is not set, the Modbus RTU Master reads registers 1 through 26, then sets the EC flag. If the EC
flag is set, the Modbus RTU Master only needs to read registers 1 through 9.
Bit 0 = External Command Flag
