Dynamic Response During Write; System Variable - Siemens SINUMERIK Series Function Manual

B3: Distributed systems - 840D sl only
2.2 NCU link
2.2.2.4

Dynamic response during write

The link variables are written with main-run synchronism. The new value may be read by the
other channels in its own NCU no later than the next interpolation cycle. It can be read in the
next part program block in its own channel.
The channels of the other NCUs in the link group normally see the new value after two
interpolation cycles. However, the limited bandwidth can lead to delays in transferring write
requests to the other NCUs in the link group (message delays). Causes for a message delay
can be:
● Writing a large number of link variables in an interpolation cycle
● Writing link variables and a the request for an axis container rotation in the same
● Writing link variables and transferring an alarm in the same interpolation cycle
2.2.2.5

System variable

NC-specific system variable
Identifier
$AN_LINK_TRANS_RATE_LAST
$AN_LINK_TRANS_RATE_LAST_SUM[<n>]
$AN_LINK_CONN_SIZE_LINKVAR
$AN_LINK_CONN_SND[<n>]
$AN_LINK_CONN_RCV[<n>]
<n>: NCU number according to MD12510 $MN_NCU_LINKNO of the relevant NCU
Note for: $AN_LINK_CONN_SIZE_LINKVAR
The writing of a link variable causes the number of bytes specified in
$AN_LINK_CONN_SIZE_LINKVAR to be transferred via the not-cyclic link communication.
The number is independent of the format of the link variables.
The maximum number of write requests that can be transferred to the specified NCU for
each interpolator cycle is calculated as:
Max. number of write requests = $AN_LINK_CONN_SND[<n>] /
$AN_LINK_CONN_SIZE_LINKVAR
90
interpolator cycle
Meaning
The number of write requests that were still free
in the last interpolator cycle.
The number of write requests that were still free
in the last interpolator cycle in the send direction
to the specified NC <n> (NCU number).
The number of bytes to be transferred for a write
request of a link variable.
The maximum number of bytes that can be
transferred per interpolator cycle from the current
NCU to the specified NCU.
The maximum number of bytes that can be
transferred per interpolator cycle from the
specified NCU to the current NCU.
Function Manual, 03/2013, 6FC5397-1BP40-3BA1
Extended Functions