11.03
3 Safety-Related Functions
3.7 Safe software cams (SN)
© Siemens AG 2003 All Rights Reserved
SINUMERIK 840D/SIMODRIVE 611 digital SINUMERIK Safety Integrated (FBSI) - Edition 11.03
3-119
3.7.1
Effects when SN reponds
!
Important
The machine manufacturer must safely logically combine the SGAs SN1-,
SN1+ to SN4-, SN4+ that are output via the NCK and PLC I/O devices in
accordance with the Safety Integrated principle, i.e. in two channels.
If a response to the cam signals is required, then the machine manufacturer
must implement this function on the basis of SGA processing. The SGAs
must be processed redundantly, i.e. in the NCK monitoring channel and drive
monitoring channel (PLC).
When defining cam positions, please note that the function only monitors the
actual position, making "predictlve" sensing of cam signals impossible.
If the "safe cams" function is active, the system timing is as follows when the
cam position is passed:
n
t
2
SN_03.DSF
t
t
3
t
4
t
5
NCK SGA
(I/Os)
611digital SGA
(axis interface)
a) Axis crosses cam
a)
t
1
Fig. 3-21
Timing when the cam position is passed
Table 3-45
Explanation of the diagram
Time Explanation
t
1
Position control clock cycle defined by the following MDs:
For 840D: MD 10050: $MN_SYSCLOCK_CYCLE_TIME
MD 10060: $MN_POSCTRL_SYSCLOCK_TIME_RATIO
t
2
Monitoring clock cycle defined by the following MDs:
For 840D: MD 10090: $MN_SAFETY_SYSCLOCK_TIME_RATIO
For 611 digital: MD1300: $MD_SAFETY_CYCLE_TIME
t
3
Time until it has been detected that the cam position has been passed (maximum 1 monitoring clock
cycle)
t
4
Conditioning time NCK monitoring channel (1 monitoring clock cycle plus a few microseconds)
t
5
Processing time, 611 digital monitoring channel
max. 1 monitoring clock cycle plus 3 IPO clock cycles plus 1 OB1 cycle; minimum 1 monitoring plus 3 IPO
clock cycles
Note:
Each axis must be measured during commissioning to determine how long it takes for cam signals to be output to the
I/O after the cam position has been passed.
Timing when cam
position is passed
