Siemens SINUMERIK 840D sl Function Manual page 856

Detailed description
2.4 Frames
2.4.5.3 Channel basic frames $P_CHBFR[n]
The number of basic frames in the channel can be configured via the machine data:
MD28081 $MC_MM_NUM_BASE_FRAMES (number of basic frames (SRAM))
The minimum configuration is designed for at least one basic frame per channel. A maximum
of 16 basic frames per channel is possible. In addition to the 16 basic frames, there can also
be 16 NCU-global basic frames in the channel.
System variable $P_CHBFR[n] can be used to read and write the basic frame field elements.
While writing a basic frame field element, the chained total frame is not activated. Instead,
the activation takes place only after a G500,G54..G599instruction is executed. The variable
is used primarily for storing write operations to the basic frame on HMI or PLC. These frame
variables are saved by the data backup.
Current channel basic frames $P_CHBFRAME[n]
System variable $P_CHBFRAME[n] can be used to read and write the current channel basic
frame field elements. The resulting total basic frame is calculated by means of the write
process in the channel. Whenever a basic frame is written, the complete basic frame is
calculated again.
Basic frame in channel $P_UBFR
The system variable is retained for reasons of compatibility, although it is redundant for the
$P_CHBFR[0] variables.
The basic frame with field device 0 is not activated simultaneously when writing to the
predefined $P_UBFR variable, but rather activation only takes place on execution of a
G500,G54,.G599instruction. For NCU global frames, the changed frame only becomes
active in those channels of the NCU, which execute a G500,G54..G599instruction. The
variable is used primarily for storing write operations to the basic frame on HMI or PLC. The
variable can also be read and written in the program.
$P_UBFR is identical to $P_CHBFR[0]. One basic frame always exists in the channel by
default, so that the system variable is compatible with older versions. If there is no channel-
specific basic frame, an alarm is issued at read/write: "Frame: Instruction not allowed" is
output on a read or write access.
Current first basic frame in the channel $P_BFRAME
The system variable is retained for reasons of compatibility, although it is redundant for the
$P_CHBFRAME[0] variables.
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 part program. The written
basic frame is immediately included in the calculation. In the case of NCU global settable
frames, the modified frame acts only in the channel in which the frame was programmed. If
the frame is to be modified for all channels of an NCU, $P_UBFR and $P_BFRAME must be
written simultaneously. The other channels must then activate the corresponding frame, e.g.,
with G54.
$P_BFRAME is identical to $P_CHBFRAME[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 allowed" is output on a read or write access.
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Basic logic functions: Axes, coordinate systems, frames (K2)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0