Type 3 message, Type 4 message – West Control Solutions N6600 User Manual
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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} ] xx aaaaa bbbbb ccccc ddddd eeeee A *
where xx is the number of data digits to follow; this is 20 for a single-control-output
instrument and 25 for a dual-control-output instrument. The digits are expressed as
shown in Table 5-1. For further information, refer to Subsection 5.3.8.4.
5.2.6 Type 3 Message
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
Controller; 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 Controller reply is of the form:
L {N} {P} {DATA} I *
(where I = Hex 49) indicating that the Controller is ready to implement the
command. If the parameter specified is invalid or is not modifiable or if the
desired value is outside the permitted range for that parameter, the Controller
replies with a negative acknowledgement in the form:
L {N} {P} {DATA} N *
5.2.7 Type 4 Message
L {N} {P} I *
This type of message is sent by the master device to the addressed slave
Controller following a successful Type 3 message transmission and reply to/from
the same slave Controller. Provided that the {DATA} content and the parameter
specified in the preceding Type 3 message are still valid, the slave Controller will
then set the parameter to the desired value and will reply in the form:
L {N} {P} {DATA} A *
where {DATA} is the new value of the parameter. If the new value or parameter
specified is invalid, the slave Controller will reply with a negative
acknowledgement in the form:
5-4
O075-5
PM-0075