Condition 1 - Siemens SIMATIC S5 ET 200U Manual

ET 200U(DP Standard): AddressAssignm.,Starting–Up, DiagnosingFaultsUsing COM ET 200
If an input/output value is read in via the process I/O image, the following
conditions may result:

Condition 1

Assumption: Failure of station 1 in the PII or in the PIQ
The CPUs 941 to 944 detect a failure of station 1 since they read in/write the
process I/O image word–by–word. Therefore, the CPUs do not read/write
address 0 in the process I/O image of station 2, although station 2 is avail-
able.
The CPU stops with timeout (if in COM ET 200 "timeout = yes"). After a
transition from STOP to RUN, the CPU switches again to RUN. Station 1 and
address 1 of station 2 are not entered in the process I/O image.
Condition 2 Assumption: Failure of station 2
PII: The CPUs 941 to 944 detect a failure of station 2 since they read in the
process I/O image word–by–word.
The CPU stops with timeout (if in COM ET 200 "timeout = yes"). The CPU
remains in the STOP mode even after a transition from STOP to RUN.
PIQ: The CPUs 941 to 944 detect a failure of station 2 since they read in/
write the process I/O image word–by–word. Therefore, the CPUs do not
read/write address 0 in the process I/O image of station 1, although station 1
is available.
The CPU stops with timeout (if in COM ET 200 "timeout = yes"). After a
transition from STOP to RUN, the CPU switches again to RUN. Station 2 and
address 0 of station 1 are not entered in the process I/O image.
Note
To avoid the above conditions, note the following when addressing CPUs
941 to 944:
1. Use load and transfer commands. These commands work on a byte–by–
2. Assign an even number as address start in a slave station (e.g. 0, 2, 4, 6,
Example Division
Example division of the digital and analog I/O areas:
of the Digital/Ana-
1. Accept "0" as the next available address for DI and DQ modules.
log I/O Areas
2. Enter "128" as next available address for AI and AQ modules.
This division corresponds to the usual SIMATIC division of the P area. How-
ever, you can separate the areas according to your needs.
5-8
byte basis and are thus able to identify the presence of each individual
byte.
...) and do not use the uneven address numbers. This enables you to ac-
cess the process I/O image.
ET 200U Distributed I/O Station
EWA 4NEB 812 6087–02b