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XTC/3 Operating Manual
Chapter 5
Remote Communications
5.1 Remote Communications Overview
XTC/3 may be remotely controlled, programmed or interrogated. This is
accomplished through remote communications and the use of a remote
command set. XTC/3 will respond to messages that contain these commands.
It will accept and operate on messages one at a time. It will respond to each
command by carrying out valid operations and/or returning a message to the
sender. A host/server relationship is established in remote communications.
XTC/3, as server, responds to the remote host’s commands.
NOTE:
Unpredictable RS-232 hardware/software combinations may occasionally
cause a command to not be recognized by XTC/3. Consequently, all
communications should include an automatic retry procedure. If a
command sent via RS-232 does not produce a response from XTC/3
within three seconds, it should be sent again.
5.1.1 Message Protocols
The message protocol serves as a structure for the contained command or
response information. It also can provide a level of acknowledgment between the
host and server and a mechanism for verifying the information content. In addition
to the optional TCP/IP interface, XTC/3 supports the following RS-232 protocols:
Standard
,
Datalog
,
XTC/2 Ck Sum
,
XTC/2 No Ck Sum
,
XTC/C Ck Sum
and
XTC/C No Ck Sum
. The
Datalog
protocol only provides for one-way transmission
of layer data from XTC/3 as described at
. The last four
protocols are intended to permit an XTC/3S or XTC/3M to respond to commands
previously sent to an XTC/2 to facilitate changeover from an XTC/2 or XTC/C to an
XTC/3 without extensive reprogramming to the external computer or PLC.
NOTE:
Unlike XTC/2 and XTC/C, XTC/3 does not support hardware handshaking.
CAUTION
Due to the reduced parameter set accessible under XTC/2
protocols, some parameters entered previously or
subsequently from the front panel, RS-232 or via TCP/IP will
be invisible to XTC/2 protocols but will remain active.
For instance, if the active process is programmed to contain
more than three layers by means other than via XTC/2
protocols, any Start command issued after layer 3 is in Idle will
execute layer 4.
NOTE:
TCP/IP will always operate using the
Standard
protocol command set.
It is not affected by the RS-232 Protocol selection.