09.95 10 Axis and Spindle Installation
10.1 Determining sampling interval and interpolation time
Notes:
• The maximum value of the basic utilization should be approx. 70%.
• Evaluation of the CPU utilization is performed in a 960 ms timebase in order to be able to
display a "stable" mean value.
How the NC CPU utilization is displayed
The value calculated for the NC CPU utilization is entered in machine data 60012. This value
is displayed in the MDD under Machine data/NC MD/General NC MD/General basic MD (for
original display see also Section 5, Section "User displays"):
Start-up/Machine data/NC MD/General NC MD
General basic MD
Measuring units
5002.4 System of units Metric
5005.4-7 Input resolution 1E-3 mm
Utilization
60012 NC CPU utilization 70%
System cycles
168 Basic drive cycle 1.00 ms
155 Position control cycle 4.00 ms
160 Interpolation cycle 16.00 ms
General basic data
5197.0 Display M active yes
... etc.
Optimization of the CPU use
On start-up of the control, it is possible to proceed as follows:
After Power On, continue with point 2 until the optimum has been found.
Comment:
On starting a part program, additional modules are active that perform the decoding of the
part program blocks. The blocks are entered in the block buffer of each channel. Depending
on the number of block buffers set (flexible memory configuration function) it takes a while
until all block buffers are full. During this time, CPU utilization is 100%. After all block buffers
have been filled, the value settles at a lower value.
1. Perform control configuration, i.e. definition of the number channels, axes and
spindles. The MD set are activated after Power On.
2. Observe the basic NC CPU utilization in the MDD display during cyclic operation.
3. Change the values for the position control and interpolation cycles: If the basic use is
small, the above cycle values can be made shorter, and vice versa.
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50 10–3
SINUMERIK 840C (IA)