Troubleshooting - Siemens SIMATIC S7 Product Information

CPU 417-4H
6. Modified Error Response
Hardware fault with one-way OB 121 call, Checksum error
In the event of hardware faults with a one-way OB 121 call and of checksum errors, a CPU
41x-4HOB behaves as described in chapter 5 of the manual "Automation System S7-400,
Fault–tolerant system" when called for the first time. The CPU response to the second
occurence of such error has been changed. This changed is described for the different CPU
modes of a CPU 41x-4H in the table below.
Errors CPU in single mode
Hardware fault OB 121 is being
with a one-way executed
OB 121 call
Checksum If two faults occur in
error two successive test
cycles, the CPU goes
to DEFECTIVE mode.
(You can configure the
length of the test cycle
in HW Config)
Note: If a second checksum error occurs in the single mode or single operation after the
double test cycle period, the CPU will respond as it did during the first error occurence.
If a second fault (hardware fault with a one–way OB 121 call, checksum error) occurs in the
redundant mode after the troubleshooting procedure, the CPU will respond as it did during the
first fault occurence.
28
CPU in single
operation
OB 121 being executed The faulty CPU goes to
If two faults occur in
two successive test
cycles, the CPU goes
to DEFECTIVE mode.
(You can configure the
length of the test cycle
in HW Config)
CPU in redundant
mode

TROUBLESHOOTING

mode. The H system
goes to single mode.
If a second fault,
triggered by the first
fault, occurs in the
troubleshooting mode,
the CPU goes to
DEFECTIVE state.
A5E00130864-03