Siemens SIMATIC ET 200SP Manual page 90

Alarms, faults and system events
8.9 Data records for diagnostics
Under error-free conditions, one master frame is sent to every available slave address for
cyclic data transfer per AS-i bus cycle. The addressed slave responds with a corresponding
slave frame. Depending on the configuration of the bus, between 1 and 31 slaves are
addressed in each AS-i bus cycle. This results in a maximum bus cycle time of 5 ms. When
two slaves with extended addressing have the same numerical address, but one is the A
address and one the B address, these two slaves are automatically addressed in two
consecutive bus cycles. It can be assumed that around 64 000 master frames are sent per
second.
Table 8- 13 Meaning of error counter
Count value / Information
Slave failure
Missing slave frame
Erroneous slave frame
I/O fault
Protocol error
Erroneous master frame
Sent master frames
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Meaning
The count value is increased when an active slave fails, that is, when process data
transmission has been interrupted. An active slave only fails when it does not
respond to six consecutive master calls.
The count value is increased when a slave does not respond to a master call or the
master does not receive the response. Transmission of process data is not
interrupted in this case.
The count value is increased when the master receives an incomplete slave
response, such as when slaves are added during operation. Transmission of process
data is not interrupted in this case.
The count value is increased when a slave signals an I/O error.
The count value is increased when the master detects a transmission error for a
slave that needs multiple cycles for transmission of data, e.g. for analog data.
The count value is incremented when a master call cannot be sent correctly, e.g. in
the event of strong interfering signals on the AS-i cable. Transmission of process
data is not interrupted in this case.
Number of master frames
This counter counts all frames sent by the master, regardless of whether or not a
slave response was received.
The total number of master frames is calculated as follows:
MT_CNT_TOTAL = (MT_CNT_HIGH x MT_CNT_BASE) + MT_CNT_LOW
The error count starts over each time the device is powered up.
By dividing the absolute values of the error counters by the number of master frames,
it is possible to calculate the percentage of errors and thus the error frequency.
AS-Interface master CM AS-i Master ST (3RK7137-6SA00-0BC1)
Manual, 07/2017, A5E02655262020A/RS-AD/004