Siemens SINUMERIK 840D sl Programming Manual page 235

$P_CHBFRAME[n] Current channel basic frames
System variable $P_CHBFRAME[n] can be used to read and write the current channel basic
frame field elements. The resulting complete basic frame is calculated in the channel as a
result of the write operation. Whenever a basic frame is written, the complete basic frame is
calculated again.
$P_BFRAME Current first basic frame in the channel
The predefined frame variable $P_BFRAME can be used to read and write the current basic
frame with the field device of 0, which is valid in the channel, in the parts program. The
written basic frame is immediately included in the calculation.
$P_UBFR is identical to $P_CHBFR[0]. The system variable always has a valid default
value. If there is no channel-specific basic frame, an alarm is issued at read/write:
"Frame: instruction not permissible".
$P_ACTBFRAME Complete basic frame
The $P_ACTFRAME variable determines the chained complete basic frame. The variable is
read-only.
$P_ACTFRAME corresponds to
$P_NCBFRAME[0] : ... : $P_NCBFRAME[n] : $P_CHBFRAME[0] : ... :
$P_CHBFRAME[n].
$P_CHBFRMASK and $P_NCBFRMASK complete basic frame
The system variables $P_CHBFRMASK and $P_NCBFRMASK can be used to select, which
basic frames to include in the calculation of the "complete" basic frame. The variables can
only be programmed in the program and read via the operator panel interface. The value of
the variable is interpreted as bit mask and determines which basic frame field element of
$P_ACTFRAME is included in the calculation.
Job planning
Programming Manual, 03/2006 Edition, 6FC5398-2BP10-1BA0
Frames
6.9 NCU global frames
6-29