HEIDENHAIN iTNC 530 HSCI Technical Manual page 1663

Hide thumbs Also See for iTNC 530 HSCI:

Table of Contents

3) Writing of PLC outputs

Time until the output states generated by the PLC program are physically

present at the terminals.

• Worst-case scenario for HSCI SW 606 42x-01:

• Worst-case scenario for HSCI SW 606 42x-02:

• Best case for HSCI SW 606 42x-xx:

• Worst case scenario for MC 42x/CC42x:

4) Overlap time

In a worst-case scenario, an overlap can occur in the HSCI system SW

606 42x-01 during reading and writing of the PLC inputs/outputs. In the

scenario described here, writing of the output states has not been

completed when reading of the next PLC cycle starts. In this case, the

output states of the preceding cycle are not yet available to the PLC program

of the subsequent cycle.

The table shows a comparison of the worst-case cycle times for reading and

writing of PLC inputs and outputs:

Reading of PLC inputs

Writing of PLC outputs

With a PLC program run time of 1.5 ms, the following, typical total times result

for the systems described here:

Worst-case scenario for HSCI SW 606 42x-01: 22.0 ms

Worst-case scenario for HSCI SW 606 42x-02: 16.0 ms

Worst-case scenario for MC 42x/CC42x: 8.25 ms

(including any interruptions of the PLC program by the interpolator)

With a typical PLC cycle time of 21 ms and using the MC 42x/CC 42x, it is

possible to write PLC outputs within one PLC cycle and to evaluate this

information again in the next PLC cycle via a PLC input. In the HSCI system

with SW 606 42x-01, however, an overlap time can occur during reading and

writing of PLC inputs/outputs in the worst-case scenario described here. This

means that an additional PLC cycle is required until updated output states are

available again to the PLC program.

HEIDENHAIN has optimized the reading of PLC inputs in HSCI systems by

6 ms as of SW 606 42x-02. Even in an HSCI system with a typical PLC cycle

time of 21 ms, PLC outputs can thus be written in one PLC cycle and the

information can then be evaluated via a PLC input in the next PLC cycle.

9.1 PLC Functions