Red Lion GEMINI 42 - Manual (Page 33)

The command string is constructed by using the above commands and value
identifiers along with the data values that are required. Data values may or may
not contain the decimal point if a decimal point is programmed into the Gemini.
The Gemini will accept the decimal points, however, it does not interpret them in
any way. Leading zeros can be eliminated, however, all trailing zeros must be
present. For example, if a Scale Factor of 1.0000 is to be sent, the data value can
be transmitted as 1.0000 or 10000. If a “1” is transmitted, the Scale Factor will be
changed to 0.0001.
The Address command is used to allow a command to be directed to a specific
unit in the Serial Communications Loop. Whenever the unit address is zero,
transmission of the Address command is not required. This is done for
applications which do not require more than one Gemini. For applications that
require several units, it is recommended that each Gemini in the loop be given a
separate address. If they are given the same address, a command such as the
Transmit Value Command, will cause all the units to respond at the same time,
resulting in erroneous data.
The command string is constructed in a specific logical sequence. The Gemini
will not accept command strings that do not follow this sequence. Only one
operation can be performed per command string. Below is the procedure to be
used when constructing a command string.
1. If the Gemini, to which the command is to be sent, is assigned an address other
than zero, the first two characters of the command string must consist of the
Address Command (N) and the address number of the unit (1-15).
2. The next characters in the command string is the actual command that the
Gemini is to perform and the value identifier if it pertains to the command. (A
command such as the Transmit per Print Options, “P”, command does not
require a Value Identifier.)
3. If the “Change Value” command is being used, the next characters in the
command string is the numerical data value.
4. The last character in the command string is the command terminator (*). This
character must be sent in order to tell the Gemini that the command string is
complete, so that they can begin processing the command.
Below are some typical examples of properly constructed command strings.
(EX. 1) Change Preset 1 on the Gemini with address of 2 to 00123.4.
COMMAND STRING: N2VA1234*
(EX. 2) Have the Gemini with address of 3 transmit the Count B value.
COMMAND STRING: N3TF*
(EX. 3) Reset Counter B of the Gemini with address of 0.
COMMAND STRING: RF*
As shown, all commands must be terminated with a “Command Terminator”
(* or 2AH). The Gemini will not process the command until the terminator is
sent. If illegal commands or characters are sent to the Gemini, they still would
need to be terminated by an (*). If they are not terminated, the next command will
not be accepted.
When writing application programs in Basic, the transmission of spaces or
carriage return and line feed should be inhibited by using the semicolon delimiter
with the “PRINT” statement. The Gemini will not accept a carriage return or line
feed as valid characters.
When a “Change Value” command is sent to the Gemini, a short amount of
time is required for the unit to process the data. This time increases with the count
rate. During this time, only one additional command may be sent to the Gemini.
This may be done 80 msec after the transmission of the “Change Value”
command. After the second command has been transmitted, the unit will ignore
any further commands until 10 msec after both the “Change Value” and second
command have been processed. It is recommended that a “Transmit Value”
command follow a “Change Value” Command. If this is done, the reception of
the data can provide a timing reference for sending another command and will
insure that the change has occurred.
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