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“PASSWORD NOT OPEN”
- If the Password in the MSM400 control unit memory is set “CLOSED”, then it will not be
possible to load data from the SAFE or OFFLINE register. The Password protects the data in the
MSM400.
“INVALID ACTION NOT THE SAME INSTRUMENT”
- If an attempt is made to transfer SAFE register data to the WORKING register of an MSM400
control unit which is not the origin of the SAFE register data, this will not be allowed. The
message indicates that D731 on the currently connected loop is not the same as the D731 in the
SAFE register.
“INSTRUMENT IN MULTIDROP MODE”
- The current output control circuitry in the MSM400 control unit is only active when the MSM400
is operating as a 0-20 or 4-20mA device. In a multidrop configuration the current is set to 4mA,
and trimming and current set commands are inoperative.
D.10.3Communication Errors
Communications between the MSM400 control unit and the SMART interface/Psion organiser are subject
to error checking and acknowledgement signals according to the HART protocol. This means that only
valid messages are accepted, and if the message is invalid then it will be rejected.
The screen of the LCD will indicate if a message has not been received correctly. This is perhaps most
likely to be seen when the Display parameters are being used, since these are updated with a new value
in a message every 0.5 seconds. If the message is received incorrectly, the second and third lines of the
display will show one of the following messages:
VERTICAL PARITY ERROR IN REPLY
OVERRUN ERROR IN REPLY
FRAMING ERROR IN REPLY
LONGITUDINAL PARITY ERROR IN REPLY
BUFFER OVERFLOW IN REPLY
Which describe the cause of the fault.
There is an identical group of errors in the outgoing message:
VERT PARITY ERROR IN OUTGOING MESSAGE
OVERRUN ERROR IN OUTGOING MESSAGE
FRAMING ERROR IN OUTGOING MESSAGE
LONGDNL PARITY ERROR IN OUTGOING MESSAGE
BUFFER OVERFLOW IN OUTGOING MESSAGE
If this occurs frequently, it is appropriate to check the electrical connections to the instrument loop, the
presence of the SMART load resistor and that the SMART Communicator is attached at the correct
position in the loop.
The “IN OUTGOING MESSAGE” group of error messages if displayed while accessing the Programme
Parameters implies that the message from the SMART Communicator was not received correctly by the
MSM400. Therefore the instructions in the message would have been rejected, and the Parameters
remain unchanged at their previous value. This previous value will be shown on the LCD screen on the
SMART Communicator after the error message, to prompt the operator to repeat the last parameter
value amendment. During a Register transfer this message will automatically cause the Communicator
to hold transmission, and suggest a retry because of the error.
The “IN REPLY” group of error messages if displayed when programming the instrument, signals a more
significant communications failure. This indicates that the acknowledgement of the change instruction
sent to the MSM400 was incorrect. It is not known whether the Parameter value in the MSM400 was
changed or not. The SMART Communicator assumes that it was not changed, and reverts to the original