Omega A2400 - Manual (Page 58)

Extended Addressing 9-6
This command will close the channel at A2400 #01 and open the channel
at A2400 #02. This is the quickest method of opening and closing A2400
channels. It also offers the least amount of data security. A2400 #01 was
closed solely upon detecting the ‘{‘ character. There is no confirmation that
A2400 #01 is closed. If A2400 #01 missed the ‘{‘ character due to noise, it
would remain open, with the possibility of two A2400’s in the open condition,
an undesirable state of affairs. This method has merit in systems with a
known clean communications channel and when speed is important.
Another variation of the implied OC command is the long form:
Command: }01
Response: *01OC1D
Single Command Module Address
Any module located on an RS-485 string may be individually addressed with
one command by appending the module command to an implied OC
command:
Command: {01$1RD
Response: *+00100.00
In this command form, the {01 is an implied Open Channel command to
A2400 #01. The ‘{‘ is also an implied Close Channel command to all other
A2400’s. It is followed immediately by a $1RD command, which is the Read
Data command for module #1 connected to A2400 #01. No response results
from the {01 portion of the command, but the $1RD data is transmitted on
the RS-485 bus. Module #1 responds back with the data *+00100.00.
Again, this command form is a trade-off between speed and data security.
It is a convenient command form to communicate with an individual module
without explicitly opening or closing an A2400 channel. This could be a good
command format to be used with noise-free data channels and where speed
is very important.
Explicit Open and Close Channel Commands
A greater level of data integrity may be obtained by using explicit forms of
the Open Channel (OC) and Close Channel (CC) commands. This simply
means that the ‘data gate’ is controlled by command sequences that require
a confirmation from the addressed A2400.