Channel-Specific Frames ($P_Chbfr, $P_Ubfr) - Siemens SINUMERIK 840D sl Programming Manual

6.9.1

Channel-specific frames ($P_CHBFR, $P_UBFR)

Function
Settable frames or basic frames can be read and written by an operator action or from the
PLC:
• via the parts program, or
• via the operator panel interface.
The fine offset can also be used for global frames. Suppression of global frames also takes
place, as is the case with channel-specific frames, via G53, G153, SUPA and G500.
Machine manufacturer
The number of basic frames can be configured in the channel via MD 28081
MM_NUM_BASE_FRAMES. The standard configuration is designed for at least one basic
frame per channel. A maximum of eight basic frames are supported per channel. In addition
to the eight basic frames, there can also be eight NCU-global basic frames in the channel.
Channel-specific frames
$P_CHBFR[n]
System variable $P_CHBFR[n] can be used to read and write the basic frames. When a
basic frame is written, the chained total basic frame is not activated until the execution of a
G500, G54...G599 instruction. 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.
First basic frame in the channel
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...G599 instruction. The variable can also be read and written in the program.
$P_UBFR
$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 permissible".
Job planning
Programming Manual, 03/2006 Edition, 6FC5398-2BP10-1BA0
Frames
6.9 NCU global frames
6-27