Special SM 335 Operating Modes
5-7
SM 335 – High-Speed Analog Input/Output Module for the SIMATIC S7-300
6ES7 335-7HG00-8BA1
Case B: Comparator time expired
The SM 335 remains in “Comparator” mode until the comparison value has been
reached or the comparator time has expired. If the comparison value is not re-
ached before the comparator time expires, the SM 335 exits “Comparator” mode
and returns to Free Cycle or Conditional Cycle mode without modifying the analog
outputs.
Case A and B
After calling the system function and switching the SM 335 to “Comparator” mode,
when only Comparator 2 is activated, the SM 335 operates as follows:
•
It measures only at one analog input (as fast as possible).
•
It suppresses and counts the end-of-cycle interrupts.
•
It compares the measured analog value with the comparison value.
Hint: If you want to output the same analog value that was output in “Comparator”
mode, change the least significant bit in the analog value’s binary code. This has
no effect on the analog value, since the least significant bit is truncated, but the
SM 335 will interpret the new binary code as a new analog value.
Note
When “Comparator” mode is exited with Comparator 2, the values at the SM 335’s
analog inputs are not current. The analog inputs are not updated until the next
measuring cycle.
Remedy: Do not read the values from the analog inputs until the next end-of-cycle
interrupt has been generated.
