Diagnostics Buffer - Siemens S7-1200 System Manual

Table 4- 17 Clock memory
Bit number
Tag name
Period (s)
Frequency (Hz)
Because clock memory runs asynchronously to the CPU cycle, the status of the clock memory can change several times
during a long cycle.
4.1.6

Diagnostics buffer

The CPU supports a diagnostics buffer which contains an entry for each diagnostic event.
Each entry includes a date and time the event occurred, an event category, and an event
description. The entries are displayed in chronological order with the most recent event at
the top. Up to 50 most recent events are available in this log. When the log is full, a new
event replaces the oldest event in the log. When power is lost, the events are saved.
The following types of events are recorded in the diagnostics buffer:
● Each system diagnostic event; for example, CPU errors and module errors
● Each state change of the CPU (each power up, each transition to STOP, each transition
To access the diagnostics buffer (Page 793), you must be online. From the "Online &
diagnostics" view, locate the diagnostics buffer under "Diagnostics > Diagnostics buffer".
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
7 6
2.0 1.6
0.5 0.625
to RUN)
5 4 3
1.0 0.8 0.5
1 1.25 2
PLC concepts
4.1 Execution of the user program
2 1
0.4 0.2
2.5 5
0
0.1
10
103