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Installation
B800-00-880 Issue D
3.7.2
Serial Enable
To send a serial message, first activate serial enable. This is achieved by linking the serial enable input signal (pin 5)
to pin 2 of the customer logic interface mating half. Edwards recommends incorporating this link into the serial
communications cable so that the serial enable is only activated when the serial cable is connected. When the cable
is removed, serial enable will become inactive.
Serial Enable acts as an interlock for start commands sent over the Serial Interface. If the pump is running in serial
control mode (having been sent a Serial Start command) and the Serial Enable subsequently becomes inactive, the
pump will trigger a fail condition and will decelerate to rest. To clear this fail condition, re-activate the serial enable
and send a serial stop command.
3.7.3
Serial protocol
The serial interface link is set to 9600 Baud, 8 bits, 1 stop, no parity with no handshaking. The commands are made
up from printable ASCII characters. The maximum message size that can be sent is 80 characters, including start and
end characters.
Note:
All alphabetical characters must be sent in upper case format. Response may contain lower case characters.
Every complete command message sent will receive a response - either a status code or a data return. The nEXT pump
can only deal with one message at a time. It will only accept a new message once the response to the previous
message has been returned.
If the nEXT pump receives characters that are not framed inside start and stop characters, it will ignore them.
Messages with the stop character missing will be discarded with no response when a new start character is received.
If the nEXT pump receives an unrecognisable message between the start and stop characters, it will return an
appropriate error message.
Refer to
Section 3.7.6
for more information about operating the nEXT pumps in multi-drop mode.
