Diagnostics Functions; Protection Mechanisms - Omron C200HW-PRM21 Operation Manuals

PROFIBUS-DP characteristics

1-4-3 Diagnostics functions

Extensive diagnostics
Device related diagnostics
Module related diagnostics
Channel related diagnostics

1-4-4 Protection mechanisms

Time monitoring
At the master
At the slave
6
Bus cycle time vs number of slaves
25.0
20.0 500
1500
15.0
3000
12000
10.0
5.0
0.0
0 4
Conditions:
Each slave has 2 bytes of input data and 2 bytes of output data.
The extensive diagnostic functions of PROFIBUS-DP enable fast location of
faults. The diagnostic messages are transmitted over the bus and collected at
the master. These messages are divided into three levels:
• Device related diagnostics
These messages concern the general operational status of the whole
device (i.e. overtemperature or low voltage).
• Module related diagnostics
These messages indicate that a fault is present in a specific I/O range
(e.g. an 8-bit output module) of a station.
• Channel related diagnostics
These messages indicate an error at an individual input or output (e.g.
short circuit on output 5).
PROFIBUS-DP provides effective protection functions against parameterisa-
tion errors or failure of the transmission equipment. Time monitoring is
provided at the DP master and at the DP slaves. The monitoring interval is
specified during the configuration.
• Protection mechanism at the master.
The DPM1 monitors data transmission of the slaves with the
Data_Control_Timer. A separate control timer is used for each slave. This
timer expires when correct data transmission does not occur within the
monitoring interval. The user is informed when this happens. If the
automatic error reaction (Auto_clear = TRUE) has been enabled, the
DPM1 exits its Operate state, switches the outputs of all assigned slaves
to fail-safe status and changes to its Clear status (see also next section).
• Protection mechanism at the slave.
The slave uses the watchdog control to detect failures of the master or the
transmission line. If no data communication with the master occurs within
the watchdog control interval, the slave automatically switches its outputs
to the fail-safe status.
Also, access protection is required for the inputs and outputs of the DP
slaves operating in multi-master systems. This ensures that direct access
8 12 16 20
Slaves
Section 1-4
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