Diagnostics with the CP 340
8.3 Diagnostics via the S7-300 backplane bus
PtP coupling and configuration of CP 340
142 Manual, 04/2011, A5E00369892-03
8.3 Diagnostics via the S7-300 backplane bus
Introduction
The CP 340 can trigger a diagnostics alarm on the assigned CPU, thus indicating a
malfunction of the CP 340. You can specify at parameterization whether the CP 340 is to
trigger a diagnostics alarm or not in the event of serious errors (see Chapter "Basic
para
meters of the CP 340 (Page 61)").
"Diagnostics
alarm = NO" is the default.
Diagnostics interrupt
In the event of a fault the CP 340 provides diagnostics information on the S7-300 backplane
bus. In response to a diagnostics interrupt, the CPU reads the system-specific diagnostics
data and enters it in its diagnostics buffer. You can read the contents of the diagnostics
buffer on the CPU using a programming device.
If a diagnostics alarm event occurs, the SF LED (red) lights up. In addition, the OB 82 is
called with this diagnostics data as start information.
Organization block OB 82
You have the option of programming error responses in the user program in the OB 82.
If no OB 82 is programmed, the CPU automatically enters STOP mode in the event of a
diagnostics alarm.
Diagnostics Information (as Bit Pattern)
The CP 340 provides 4 bytes of diagnostics information. To display the error that has
occurred, these bytes are occupied as follows:
2nd byte:
The 2nd byte of diagnostic data contains the class ID of the CP 340 in bits 0 to 3.
2. byte
7 6 5 4 3 2 1 0
0 0 0 0 1 1 0 0
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