Unit Settings
Section 5-1
58
5-1-4
Fatal PLC error handling
DM m+17 defines the handling of fatal PLC errors. The Unit will react on a
falling edge of Run bit IR n.00. The Run bit will turn OFF in case of:
•
a fatal error in the PLC system, e.g. Memory error, I/O bus errors.
•
a system FALS error.
•
a user-generated FALS error.
•
a PLC CPU mode change to/from Program mode.
If any of these situations occur, the remote outputs will be switched to a user-
defined state. If the data exchange mode (selected with DM m+16) is
asynchronous, DM m+17 allows the user to choose between:
CLEAR outputs:
The output data in the Output buffer is cleared and transmitted to the slaves
(if communication is not inhibited).
HOLD outputs:
The output data in the Output buffer is not transmitted to the slaves anymore;
the outputs of the slaves remain the previous state.
DM word
Value
Meaning
m+17
Fatal PLC error handling (asynchronous data exchange mode)
0000
CLEAR outputs
other
HOLD outputs
Note
This selection is ONLY valid when the Unit operates in the asynchronous data
exchange mode (i.e. DM m+16 = 0000). Even if program execution stops,
fieldbus communication is maintained by the Unit, independent of the PLC
cycle.
In synchronous data exchange mode, when program execution stops, no
fieldbus cycles are triggered. Therefore the remote output status cannot be
maintained. The status of PROFIBUS-DP will automatically change to
CLEAR, followed by STOP. All outputs will be cleared automatically, even if
DM m+17 specifies to hold the outputs!
The Unit is not able to distinguish between a user-controlled reset of the IR
n.00 bit and a reset due to a fatal PLC error. Both are handled in the same
way. Be aware that changing the to/from Program mode will also reset IR
n.00. In Program mode, it is possible to force IR n.00 to the ON state, so that
remote I/O can be operated for debugging and commissioning.
!
Caution
Содержание C200HW-PRM21
Страница 1: ...C200HW PRM21 PROFIBUS DP Master Unit OPERATION MANUAL Cat No W349 E2 2...
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Страница 5: ...C200HW PRM21 PROFIBUS DP Master Unit Operation Manual Produced May 2000...
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Страница 126: ...Authorised Distributor Cat No W349 E2 2 Note Specifications subject to change without notice Printed in the Netherlands...