12
ASCII
RS485/RS232 Communications Interface
Response to a `Set Parameter’ Message
The Drive will respond to a Set Parameter message in one of three ways:
1.
Positive Acknowledgement (ACK)
2.
Negative Acknowledgement (NAK)
3.
No Reply: Under certain circumstances the supervisor may not receive a reply from the
Drive. This could be due to any of the following reasons:
•
Group/Unit address
identifiers not
recognised.
•
An error (e.g. parity)
is found in one or
more of the
characters up to and
including (ENQ).
•
Communications
loop failure perhaps
due to noise or
wrong Baud Rate
being selected.
•
Hardware failure.
•
Serial link is
disabled on the
Keypad.
In these cases the
supervisor should be
programmed to "time-
out", i.e. wait for a
response for a short
time (160 msec
minimum) before trying
again.
Figure 1 Drive Response Sequence to an ASCII Selection Message
Further Transmission and/or Termination
Further Transmission
If the supervisor still has an established connection with the device, you can repeat the previous
message without re-establishing connection.
In both cases, writing to or reading from the device, you can use this to re-select the previous
parameter or to select the next parameter in the parameter list. Refer to “Transferring Data -
ASCII Example Messages”, page 19 for further explanation.
Termination (EOT)
If you wish to terminate connection with a particular device and establish connection with
another, send the 'Establish Connection' sequence preceded by the (EOT) control character,
(End Of Transmission).
The (EOT) character resets all devices on the data link to be responsive to the next four
characters, i.e. the (GID)(GID)(UID)(UID) address.
In 2-wire operation, an (EOT) can only be sent when the supervisor has Master status.
SEND
MESSAGE
PARITY CHECK
VERIFY CHECKSUM (BCC)
VERIFY THAT (C1) (C2)
ARE A VALID MNEMONIC
AND CAN BE WRITTEN TO
OK
OK
FAIL
FAIL
FAIL
FAIL
OK
MESSAGE
RECEIVED
VERIFY DATA (D1)..(Dn)
IS VALID AND NOT
OUT-OF-RANGE
OK
FAIL
(NAK)
NEGATIVE
ACKNOWLEDGEMENT
(ACK)
POSITIVE
ACKNOWLEDGEMENT
UPDATE THE
SELECTED PARAMETER
WITH THE NEW VALUE
CONTAINED IN THE
MESSAGE
No Reply
OK
Summary of Contents for 6513
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