Data Exchange with the SM 335
3-25
SM 335 – High-Speed Analog Input/Output Module for the SIMATIC S7-300
6ES7 335-7HG00-8BA1
Note
For reasons of compatibility with older module versions, the SM 335 has two
comparator modes.
Comparator mode is set via bit 4:
Bit 4 = 0: Mode 0 (comparator 1 and comparator 2 work on one measuring
channel only; this mode should only be used for reasons of compatibility with older
module states.)
Bit 4 = 1: Mode 1 (comparator 1 and comparator 2 work on different or the same
measuring channels – see Figure 3-6, Bit 3 to Bit 0.)
With comparator mode 0, the bit assignment in Figure 3-6 changes (Bit 3 to Bit 0)
as follows:
• 0001 – Analog input CH0
• 0010 – Analog input CH1
• 0100 – Analog input CH2
• 1000 – Analog input CH3
Comparator check byte (DR1, byte 12)
You can additionally check the comparator in the comparator check byte: The
comparator check byte has the following structure:
76543210
Analog output CH0
Analog output CH1
Analog output CH2
Analog output CH3
Direction
Comparator 1
Comparator 2
Hardware interrupt
Fig. 3-7 Comparator Check Byte for “Comparator” Mode
Direction (DR1, bit 12.7)
If bit 7 in the comparator check byte is set to ’0’, the comparison is made in the
direction of rising analog values.
If bit 7 is set to ’1’, the comparison is made in the direction of falling analog values.
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