Direction (Ds1, Bit 12.7); Comparator 1 And Comparator 2 (Ds1, Bit 12.6 + 12.5); Pral (Ds1, Bit 12.4); Comparator 1 To Comparator 2 Switchover Point - Siemens SIMATIC S7-300 Manual

Data exchange with SM 335
3.3 Modifying SM 335 parameters in RUN

Direction (DS1, Bit 12.7)

If bit 7 of the comparator check byte is set to '0', the comparison is carried out in direction of
ascending analog values.
If bit 7 is set to '1', the comparison is carried out in direction of descending analog values.

Comparator 1 and Comparator 2 (DS1, bit 12.6 + 12.5)

The comparator 1 and 2 bits are used to enable comparator 1 and 2.
Table 3- 13
Bit 6
1
0
1
0

PRAL (DS1, bit 12.4)

If you set bit 4 in the comparator check byte to '1', SM 335 generates a hardware interrupt at
the switchover point.

Comparator 1 to Comparator 2 switchover point

Comparator 1 is monitored in the free or conditional measuring cycle. After the measured
value has reached or exceeded the value of Comparator 1 and a Comparator 2 was defined,
only the channel of Comparator 2 is measured cyclically (at intervals of approx.. 40 µs),
starting from the switchover point.
The free or put additional measuring cycle is resumed after the measured value has reached
or exceeded the value of Comparator 2, or if the parameterized watchdog timeout (max. 8.3
seconds) has been exceeded.
Analog output (DS1, bits 12.3 to 12.0)
Use bits 0 to 3 of the comparator check byte (DS1, byte 12, see the figure comparator check
byte for the special mode "Comparator") to specify at which outputs the analog values
defined in DS1 (bytes 0 to 5 in the table of data set 1 of SM 335 for the special mode
"Comparator") are to be output.
● Bit i = 1: the specified value is output
● Bit i = 0: the old analog value is retained
You can set up to 3 bits. The analog values are output until a new value is written to the
output.
56
Checking comparator with check bits and 2
Bit 5 Behavior of the comparator
1 Enabling comparators 1 and 2 in succession
1 Enabling comparator 2
0 Enabling comparator 1
0 The special mode "Comparator" is terminated immediately.
SM 335 - High-speed analog mixed module for SIMATIC S7-300
Manual, 02/2009, A5E02409063-01