Siemens SIMATIC Manual page 426

Analog modules
6.11 Analog input module SM 331, AI 6 x TC isolated (6ES7331-7PE10-0AB0)
Short-circuit to M or L
The module does not suffer any damage if you short-circuit an input channel to M or L. The
channel continues to output valid data and does not report a diagnostics event.
Special features of channel groups with respect to hardware interrupts when limit is exceeded
You can set the high and low limits triggering hardware interrupts separately for each
channel in STEP 7.
Hardware interrupt
The table below shows the contents of the 4 bytes of additional OB40 information during a
hardware interrupt.
Content of the 4 bytes with additional information
Special 2 bits per channel to identify the range
analog flags
High limit exceeded at channel
Low limit undershot at channel
Free byte
Free byte
Startup characteristics and compensation time monitoring (watchdog) for external cold spot
compensation via remote thermoresistor
When the module starts up, all inputs report an overflow (32767). Once a compensation
value has been received via data record 2, the module starts to read the TC inputs and to
output correct data. If the module does not receive any data from data record 2 within
5 minutes of startup, a reference channel fault is reported in the standard channel
diagnostics data. If enabled, a diagnostic interrupt is sent.
The module features time monitoring (watchdog) set to 5 minutes, which is reset when a new
compensation value is received via data record 2. If the module does not receive any data
from data record 2 within the 5 minute interval set for the time-monitoring function in normal
operation, a reference channel fault is reported in the standard channel diagnostics data. If
enabled, a diagnostic interrupt is sent.
Internal calibration while the process is running
The module can compensate most of the internal temperature-drift errors. Internal calibration
while the process is running is always executed after startup, when parameters are
reassigned, and when the power is switched on/off. Once the relevant parameters have
been activated, internal calibration while the process is running is also performed if the
ambient temperature at the module changes by 5 degrees Celsius. Enabling calibration while
the process is running interrupts the module I/O cycle until calibration is complete. The
duration of the interruption depends on the programmed interference frequency; see the
table below for information about this relationship.
426
2 7 2 6 2 5 2 4
5 4
5 4
2 3 2 2 2 1 2 0
3 2 1 0
3 2 1 0
S7-300 Module data
Manual, 06/2017, A5E00105505-AJ
Byte
0
1
2
3