Siemens SINUMERIK 840D sl Function Manual page 469

Wait mark 1 is set in Channels 2 and 3
Channel 2 proceeds with additional processing and program processing in Channel 3 is
stopped because of read-in disabled.
This behavior can be transferred to all available channels.
Extended Functions
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
K5: Mode groups, channels, axis interchange
6.3 Channels - only 840D sl
469