Siemens SINUMERIK 840D sl Function Manual page 129

Note
A delay time between STOP F and STOP B should only be set, if, during this time, an alternative
response is initiated by evaluating the system variables $VA_XFAULTSI and $A_XFAULTSI.
Further, when using the delay time, a monitoring function should always be active - also in the
automatic mode (e.g. SE, SN, SG with high limit switch). For example, if the SBH monitoring
function is only active on the drive side, for example because of the (single-channel) failure of
a door switch, then although this results in a STOP F, the STOP F - STOP B delay time on the
NCK side is not started if previously no monitoring function was active. This means that in this
case, the drive responds with a STOP B (however this is also initiated in the NCK due to the
interchange of the stop responses), but this is not displayed in the NCK variables
$VA_XFAULTSI and $A_XFAULTSI.
The appropriate monitoring functions of the drive (e.g. when SBH is selected) are also executed
instantaneously without any delay.
Note
The drive-based ESR can be initiated by writing to system variable $AN_ESR_TRIGGER. The
STOP F delay time in MD36955 $MA_SAFE_STOP_SWITCH_TIME_F or drive parameter
p9555 should be selected, so that the timer for ESR in p0892 is covered by the SINAMICS
basic system.
See also Chapter "Delayed pulse cancellation in the event of communication failure
(Page 758)".
Comment:
When combined with "ESR managed from the control", theoretically the following error is
possible: Both monitoring channels (NCK and drive) trigger a STOP F; however, a safety
function is only active on the drive side (errors in the two SPL channels, which are then most
probably responsible for the STOP F). In this case, the NCK does not trigger an ESR, because
for the NCK no subsequent STOP B can be identified. Conversely, this statement is also valid
for the combination with "ESR integrated in the drive" and a safety function is only active in
the NCK. The ESR integrated in the drive is then not started.
Example 1 - delaying the transition from STOP F to STOP B
The speed characteristic of an axis for parameterized stopping is shown in the following
diagram. In this case, the axis should continue 500 ms and then brake along the parameterized
ramp. A delay time of 2.5 s is selected until STOP B is initiated
($MA_SAFE_STOP_SWITCH_TIME_F).
Safety Integrated
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Safety functions integrated in the system/drive
7.3 Safe Stops A-F
129