Edwards nEXT 55, Instruction Manual

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can be received, which can move the pump to parallel control mode or serial control
mode. Serial start commands can be received only if the serial enable line is active.
The state of the serial enable line can be switched between active and inactive while in
mixed parallel and serial operation. The primary function of the serial enable line is to
enable the serial link. It has no direct effect on the control mode. The pump will receive
and respond to serial commands whenever the serial enable line is active. The pump will
not receive or respond to serial commands when the serial enable line is inactive.
Availability of the parallel standby and fail signals depends on the state of the serial
enable line and the position of the RS485/RS232 switch as given in Table: Serial enable
matrix .
Table 29
Serial enable matrix
Switch Serial enable active Serial enable inactive
RS232
Standby and fail lines are used for
RS232 data.
Standby and fail lines are used for par-
allel Standby control and fail indica-
tion.
Parallel standby control and fail indi-
cation are disabled.
Serial communications are disabled.
RS485
Standby and fail lines are used for
RS485 data.
Standby and fail lines are in (RS485)
high impedance state.
*
Parallel standby control and fail indi-
cation are disabled.
Serial communications are disabled.
* Pump target speed will switch between run speed and standby speed in response to
data driven onto the RS485 bus by other devices connected to the bus. It is not
recommended to activate the parallel start line with the RS485/232 switch in RS485
position and serial enable Inactive. Deactivation of the serial enable line is not
recommended with the pump running following a start from the parallel start line when
the RS485/232 switch is in the RS485 position.
In parallel control mode, the pump does not accept serial stop commands but will
accept all other serial commands. When serial enable is active, the pump will operate at
standby speed if the serial standby command is given.
The pump will operate at standby speed when:
▪ Serial enable is inactive
▪ RS485/RS232 switch is in RS232 position and
▪ parallel standby line is active.
In serial control mode, the state of the parallel Start line will be ignored but the serial
enable line gives an interlock function as shown in Figure: Serial and parallel control
flowchart . This interlock function only operates with serial start commands and in serial
control mode only. In serial control mode, the pump cannot be commanded to standby
speed by the standby line, instead a serial standby command must be used.
The parallel normal and analogue output signals give valid pump status information at
all times under mixed parallel and serial operation. The analogue output voltages are
given in Table: Logic interface technical data .
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