Instruction manual

1070 072 163-101 (97.11) GB
BT20 Menu Descriptions 8-7
8.3.3 Explanation of Terms
First-value Error
A system runs fault-free if all cascade sequences contributing to the op-
eration (a maximum of 60) are processed without error. If an error occurs
in a cascade, it is recognized by the controller. As this error comprises the
first error in the course of system sequence processing, it is declared the
first-value error (also known as first-up value error).
Secondary Fault
As a rule, the consequence of the occurrence of a first-value error in the
system will give rise to the occurrence of additional cascade faults. These
faults are referred to as secondary faults. Because normal system opera-
tion can often be restored by remedying only the first-value error, secon-
dary faults are generally deemed to be of minor importance.
Fault Entry Criteria
There are two options for triggering a fault entry in the cascade sequence.
Monitoring Time
Each step of a cascade sequence is allocated to a default function. While
the respective function can be a movement of the system, it may also
comprise the preparation for additional movements. A measurable time
interval is attached to each function. The monitoring time is used to con-
trol this interval, and a fault entry is generated as soon as the time interval
is exceeded.
Fault Marker
In the case of time-critical faults, e.g. with the opening of safety-
interlocked protective system doors, there is little usefulness in utilizing
the monitoring time interval.
In such cases, the occurrence of a fault will cause an immediate reset of
the fault marker, triggering an instant fault entry.
Further Linking of BEFA or WSB Marker
In order to process a step for the subsequent display in the BT5 operator
terminal, or for the display of the ladder diagram in the monitor (of the PG
programming device), or for documentation purposes, it is required to use
the BEFA or WSB marker as an AND starting condition for a new branch.
For display in the operator terminal, the pointer for the BEFA of WSB
marker must occur after 17 AND links, and for the ladder diagram the
same applies after 7 AND links.
Permitted Operands and Address Ranges
Operand Address range, ZE200 Addr. range, ZS400/500 Address range, ZS501
Inputs I I0.0 through I23.7 I0.0 through I63.7 I0.0 through 127.7
Outputs O O0.0 through O15.7 O0.0 through O63.7 O0.0 through O63.7
Markers M M0.0 through M191.7 M0.0 through 255.7 M0.0 through 255.7
Timers T T0 through T127 T0 through T127 T0 through T127
Counters C C0 through C63 C0 through C127 C0 through C127
Special markers SM not available SM0.0 through SM31.7 SM0.0 through SM31.7
Fig. 8-6 Permissible Address Ranges