Siemens SINUMERIK 880 SW 6 Planning Manual page 193

05.91
EXTERNAL EXECUTION
1 signal: The "External execution" function is activated when the signal is set. The part
program for the NC channel is read in at an interface during machining.
0 signal: The "External execution" function is not active or is deselected. The part program
is executed normally from the part program memory in the COM area.
Notes:
• The "External execution" function can be selected by the user by softkey (see EXTERNAL
EXECUTION SELECTED signal) or automatically by the PLC user program.
• The interface to be used is specified in machine data MD 130*. If this interface is already
busy when the function is initiated (by NC START), alarm 2044 "Error external execution"
is issued.
• If "External execution" is initiated by a host computer, the PLC user program must
evaluate errors when the function is started and report to the host.
• If the external part program is executed faster than it is transmitted so that the subsequent
block is not available, workpiece machining comes to a standstill. The PLC user program
has recourse to the following options in order to prevent this in conjunction with time-
critical program sections:
– General reduction of machining feedrate (feedrate override)
– Ensure that the buffer for incoming program parts is full before time-critical program
sections, e.g. by means of read-in disable. The buffer size and free capacity can be
queried from the NC data channel.
Time-critical program sections can be marked, e.g. by special M functions, so that the PLC
user program is able to recognize them.
©
Siemens AG 1991 All Rights Reserved
SINUMERIK 880 (PJ)
6 NC Channel/PLC Interface (DB 10 ... DB 25)
6ZB5 410-0HE02
6.4.4 Program modification
DW 2, bit 15
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