
COMMUNICATION
MULTI GAUGE CONTROLLER
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Error
code
Error type
Description
x
Busy
/
Message
discarded
The server (Slave) is busy for long time with processing the pro-
gramme commands. The Client (Master) should try again to send the
message later, when the server (Slave) is free.
x
Not
ac-
knowledge
The response of the device inquired when the required action cannot
be executed.
x A
Network
path
un-
available
Applies to network gates. It indicates that the network gate cannot
allocate an internal communication path from the input port to the
output port to execute the command.
x B
No response
Applies to network gates. This means that no response has been re-
ceived from the target device. It usually means that the device is not
present in the network.
Table . : Erros codes
. .
TYPE OF DATA USED IN COMMUNICATION
One of the main limitations of the Modbus protocol is the fact that the device memory is visible
as a variable
-bit integral numbers table. In most cases it is suf icient, because scaling to the
appropriate value without losing precision can be used. In fact it has a disadvantage consisting in
the fact that the scaling factor must be known for the devices at both ends of the communication
link.
The next problem are variables, for which -bit representation is not suf icient, e.g. value of vac-
uum. To solve these problem, different types of variables have been implemented in the MG ,
enabling the full resolution of data.
The most precise data type is -bit loat in the ”IEEE-
” standard. This format is written in the
memory as two consecutive words ( bytes) in the order: “MSB irst”. The rules determining the
organisation of data in two consecutive words depends on the type of a given parameter.
Other data types used in the Modbus protocol variables:
• Enumerating parameters are parameters, which have their own text representation in the
user interface, e.g.: “Type of gauge:” - ”CTR , TTR , TTR
,...”, etc.
• Parameters of ”bool” type are parameters which may be ” ” or ” ”. These parameters are
described in the table as “bool”.
• Parameters of ”integer” type are integral parameters, without decimal points. They include
parameters such as “Degassing power” or “Sensitivity”. They can be - or -bit parameters
and are marked in the table as ”uint ” or ”uint ” for integer numbers without sign and ”int ”
or ”int ” for integer numbers with sign.
• Parameters of ” loat” type are parameters with a decimal point. These are parameters such as
“Vacuum value” or “Setpoint” settings. These parameters are marked in the table as ” loat ”
and their writing is compatible with the -bytes ”IEEE-
” standard.
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