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14.2.4
Loop-Through Mode (OP17 only)
Connection
Configuration
Scheme
Constraints in
loop-through
mode
Particularities for
connection of a PU
14-8
The IF1 interface of the OP17 is optionally available for the loop-through
mode of a configuration computer (PU or PC). This enables communication
between the PU or PC and the PLC via the OP17.
Standard cables are available for the connections in AS511 loop-through
mode shown in Figure 14-4 (refer to the ST80.1 catalog).
OP17
IF2
IF1A/B
Figure 14-4 Connnection Configuration Scheme for AS511 Loop-Through Mode
Print functions of the looped-through OP cannot be used.
The OP does not perform life-bit monitoring, i.e. it cannot detect whether
the PLC is in Stop mode, for example. Life-bit monitoring continues to be
performed on the PLC.
System performance may deteriorate due to higher loading of the inter-
face to the PLC.
If PU status functions are activated (message on PU: "Status processing in
progress " – for example, for STATUS VAR, FORCE VAR),
the following system message is displayed on the Operator Panel
"$340 Status in progress, loop- through mode",
the OP can no longer be operated,
communication between the OP and the PLC is stopped. There is there-
fore little sense in evaluating error number 115 of the standard FB on the
PLC in this particular instance.
Upon termination of status functions by means of the ESC key on the PU, OP
functions are resumed.
If "Apply" is pressed once only with Force VAR after a value has been
entered, the value you entered is transferred to the PLC, and the status
function of the PU is still not active. This value (for example, a message bit
or an actual value) can still be read by the looped-through OP and processed
(for example, display of the associated message or the actual value). Not
until "Apply" is pressed a second time is the PU status function activated.
TTY passive
RS232
PLC
Equipment Manual OP7, OP17
PC/PU 7xx
COM1
(25-pin)
Release 04/99
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