Siemens SINUMERIK 840D sl Function Manual page 179

The following steps are illustrated:
● 1.1 Position control on NCU1 reads in actual values of leading value axis from the drive
● 1.2 In the same cycle as (1.1), the actual values from the NCU1 interpolator are written to
● 1.3 NCU1 interpolator writes the generated setpoints of the leading value axis to the link
● 2. Setpoints and actual values are transferred from NCU1 to NCU2 via the link module.
● 3.1 NCU2 interpolator receives setpoints of the leading value axis via the link module and
● 3.2 NCU2 interpolator writes the generated setpoints of the following axis in the buffer for
● 3.3 NCU2 interpolator sends reaction feedback of following axis to leading value axis to
● 4.1 NCU1 position control receives setpoint for leading axis (delay caused by:
● 4.2 Reaction feedback is transferred from NCU2 to NCU1.
● 5. NCU1 interpolator receives reaction feedback and can incorporate it when calculating
Transporting lead link data
The system variables $AA_LEAD_SP and $AA_LEAD_SV (see below) are transferred via
the acyclic service. These system variables have a lower transfer priority than the link
variables.
Approx. 320 bytes of data are exchanged for the lead link axis (setpoints and actual values).
The communication time required for this operation is approx. equal to that required for a link
axis.
In contrast to local NCU coupling, the leading axis setpoints (on NCU1) with cross-NCU
couplings are delayed to achieve synchronously clocked assignments of setpoints for the
leading/following axis. (See step 4.1)
The set interpolation cycle must be identical for all lead link NCUs in the axis grouping.
Axis replacement
The channels of the NCU that is driving the following axes are not allowed to traverse or
replace a lead link axis. The real leading axis can be replaced on its home NCU.
The commands GET, GETD and also Auto-Get ( $MA_AUTO_GET_TYPE) are rejected by
the alarm "Channel %1 axis replacement for axis %1 not allowed".
Extended Functions
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
Several Operator Panels on Several NCUs, Distributed Systems (B3)
and writes them in the communication buffer for interpolation.
the link module.
module and in the local buffer for position control.
calculates the setpoints of the following axis.
position control.
the link module.
MM_SERVO_FIFO_SIZE=4). NCU2 position control receives setpoint for the following
axis.
setpoints for the leading value axis.
2.11 Lead link axis
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