Lenze ETC Motion Control - Manual (Page 202)

Machine constants
Storage space reservation
MK_LAH_VORLAUFTIEFE
4
4.4
4.4.7
l
202 EDSTCXN EN 2.0
4.4.7 MK_LAH_VORLAUFTIEFE
This machine constant defines the maximum number of orders in the
prebuffer. The prebuffer is a circular puffer (FIFO) between DIN interpreter
and rough interpolator and is used to isolate the interpretation from the
execution of DIN blocks. This MC defines how many blocks can be seen in
advance during the processing of a DIN program.
The MC contains one parameter for each possible NC channel.
The minimum value of this MC is 8 blocks. The entered value should be a
power of two (8, 16, 32, 64, 128, ...). If not, it is internally rounded up to the
next higher power of two.
The prebuffer is assigned resources in the main memory, namely approx.
1500 byte per block. If the size of the memory is insufficient for installing the
prebuffer, a corresponding error message is generated when restarting the
control and the prebuffer is reduced to the minimum size of 8 blocks.
Please also read chapter "Block preprocessing and time synchronization" in
chapter "CNC programming" (
¶ 90).
4.4.8 MK_LAH_RUECKLAUFGRENZE
This machine constant defines the maximum number of blocks which can be
interpolated backwards in a program. These blocks are stored in the
prebuffer and reduce the predepth, see above.
The MC contains one parameter for each possible NC channel.
The value in this MC must not exceed MK_LAH_VORLAUFTIEFE−8.
Otherwise, the return limit is limited to this value and an error is reported.
)
Note!
The number of blocks to be interpolated backwards is also
limited by other factors. In general, the backward interpolation
stops when no more interpolation blocks are available. It stops
as soon as a function occurs which is not a pure interpreter
function and cannot be inserted in the previous or subsequent
block, e.g. an individual M function, which is not preceded by a
traverse block or a traversing block with M or Q function.
(
¶ 174).
Please make sure that M functions are output by default during
backward interpolation, but no Q functions.