Siemens SINUMERIK 840Di Function Manual page 553

Function
When Start disable is set, no new program starts are accepted for the selected channel.
Start attempts are counted internally.
If a start is executed by the PLC before a global block disable is sent from the HMI to the
NCK, the program is not stopped by the Start disable and its status is transmitted to the HMI.
NC Start disable and global Start disable have the same effect on the internal counter for
starts that have been sent but not executed. (OPI variable startRejectCount).
Bypassing global Start disable
The interface signal:
DB21, ... DBX7.5 (PLC → NCK)
allows the PLC to temporarily bypass a global Start disable.
0:
1:
Messages
If desired, a message can be issued when a Start attempt occurs while a global block
disable is active.
The control is exercised using machine data:
MD11411 $MN_ENABLE_ALARM_MASK Bit 6
1:
0:
2.4 Program test
2.4
Testing part programs
Purpose
Several control functions are available for testing a new part program. These functions are
provided to reduce danger at the machine and time required for the test phase. Several
program functions can be activated at the same time to achieve a better result.
Mode Group, Channel, Program Operation, Reset Response (K1)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Global Start disable is effective.
Global Start disable is temporarily canceled.
Alarm 16956 appears: Channel %1, Program %2 cannot be started because of "Global Start
disable".
Start attempts when a global block disable is set are not signaled by an alarm.
Detailed Description
2.4 Program test
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