A735-01-860 Issue A
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Connection for serial control and monitoring
Figure 4 - Logic interface connections - RS485 serial control
3.2 Serial enable
To send a serial message you must first activate serial enable. This is achieved by linking the serial enable input signal
(pin 5) to pin 2 of your logic interface mating half. We recommend that you incorporate this link into your serial
communications cable so that the serial enable is only activated when the serial cable is connected. When you
subsequently remove the cable, serial enable will become inactive.
Serial enable acts as an interlock for start commands sent over the serial interface. If the nXDS pump is running in
serial control mode (having been sent a serial start command) and the serial enable subsequently becomes inactive,
the nXDS pump will trigger a fail condition and will decelerate to rest. To clear this fail condition, you must re-
activate the serial enable and send a serial stop command.
3.3 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 you can send is 80 characters, including start and end
characters.
All alphabetical characters must be sent in upper case format. Response may contain lower case characters.
Every complete command message you send will receive a response - either a status code or a data return. The nXDS
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 nXDS 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 nXDS pump receives an unrecognisable message between the start and stop characters, it will return an
appropriate error message.
1. RS485 interface on control equipment or PC
2. nXDS pump logic interface
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