
B-63494EN/02 3.SAFETY FUNCTIONS
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3.4 SAFE-RELATED I/O SIGNAL MONITORING
A set of safe-related I/O signals are connected to the I/O Link and the
servo FSSB through separate paths. The two independent CPUs
individually check the input signals. If a mismatch between two
corresponding signals is found, the system enters the safe stop state.
The following safe-related I/O signals are monitored or output in
redundant mode:
• Emergency stop input signal
• Protective door state input signal
• Lock state input signal
• Input signal for monitoring the MCC contact state
• Programmable safe-related input signals
• Safety speed/safety position selection signal input
• Output signal for turning off the MCC (power-down)
• Programmable safe-related output signals
• Safety position switch signal output
To configure the 2-path system, the machine tool builder must connect
these signals to both the I/O module and the FSSB I/O.
IMPORTANT
If the safety input signals, except for emergency
stop input signals, are connected to the I/O module,
a Ladder program must be created to establish a
1-to-one relationship between the actual input (X)
and the input to the CNC (G).
The duplicated input signals are always checked for a mismatch,
regardless of whether the safety function is active or not. When a
signal state changes, the pair of signals may not match for some period
because of a difference in response. The dual check safety function
checks whether a mismatch between the two signals continues for a
certain period of time, so that an error resulting from the difference in
response can be avoided. The check period must be specified as a
safety parameter.
Parameter No. Name
1945 Safe-related input signal check timer
The following signals are not defined as safe-related I/O signals and
are not duplicated. The signals, however, are necessary for the system.
• Input signal for making a protective door open request
• Input signal for starting the test mode
• Output signal for specifying a command to lock the protective door
• Output signal for requesting a MCC off Test