Filter
Top Products
4.2.1 Type 1 Mes sage
L {N} ? ? *
This message is used by the master device to determine whether the addressed slave
is active. The reply from the slave instrument, if it is active, is
L {N} ? A *
An inactive instrument will give no reply.
4.2.2 Type 2 Mes sage
L {N} {P} {C} *
This type of message is used by the master device to interrogate or modify a parameter
in the addressed instrument. {P} identifies the parameter (as defined in Table 4-2) and
{C} represents the command to be executed, which may be one of the following:
+ (Hex 2B) - In cre ment the value of the pa rame ter de fined by {P}
– (Hex 2D) - Dec re ment the value of the pa rame ter de fined by {P}
? (Hex 3F) - De ter mine the cur rent value of the pa rame ter de fined by {P}
The reply from the addressed instrument is of the form:
L {N} {P} {DATA} A *
where {DATA} comprises five ASCII-coded digits whose format is shown in Table 4-1.
The data is the value requested in a query message or the new value of the parameter
after modification. If the action requested by the message from the master device would
result in an invalid value for that parameter (either because the requested new value
would be outside the permitted range for that parameter or because the parameter is
not modifiable), the instrument replies with a negative acknowledgement:
L {N} {P} {DATA} N *
The {DATA} string in the negative acknowledgement reply will be indeterminate.
Scan Tables
A parameter identifier character “]” in the message from the master device indicates
that a “Scan Table” operation is required. This provides a facility for interrogating the
values of a group of parameters and status in a single message from the master
device. The reply to such a command would be in the form:
L {N} ] 25 aaaaa bbbbb ccccc ddddd eeeee A *
The digits aaaaa, bbbbb etc. are expressed as shown in Table 4-1. For further
information, refer to Subsection 4.3.17.
4.2.3 Type 3 Mes sage
L {N} {P} # {DATA} *
This message type is used by the master device to set a parameter to the value
specified in {DATA}. The command is not implemented immediately by the slave
instrument; the slave will receive this command and will then wait for a Type 4 message
(see below). Upon receipt of a Type 3 message, if the {DATA} content and the specified
parameter are valid, the slave reply is of the form:
4-4 November, 2000 OM067-4
Sec tion 4
1
8
-DIN Digi tal In di ca tor 59039
RS485 Se rial Com mu ni ca tions Product Man ual - Vol ume I