Analog modules
6.12 Analog output module SM 332; AO 4 x 16 bit; isochronous; (6ES7332-7ND02-0AB0)
S7-300 Automation System Module data
6-114 Manual, 08/2006, A5E00105505-04
6.12.3 Isochronous mode
Properties
Reproducible reaction times (i.e. of the same length) are achieved in a SIMATIC system by
means of a constant DP bus cycle, and synchronization of the single cyclic processes
outlined below:
● Cyclic user program execution. The length of the cycle time may vary due to acyclic
program branching.
● Independent and variable DP cycle on the PROFIBUS subnet
● Cyclic operation of the backplane bus of the DP slave.
● Cyclic signal conditioning and conversion at the electronic modules of the DP slave.
The constant DP cycle runs in synchronism and at the same length. The CPU run levels
(OB61 to OB64) and isochronous IO are synchronized with this cycle. I/O data are therefore
transferred at defined and constant intervals (isochronous mode.) Maximum oscillation of
±50 μs.
Requirements
● The DP master and slave must support isochronous mode. You require
STEP 7
V5.2 or
higher.
Mode of operation: Isochronous
Conditions of isochronous mode:
Processing and activation time T
WA
between reading the output value to the
transfer buffer and loading it into the D/A converter for output
750 µs
T
DPmin
1100 µs
Diagnostic interrupt max. 4 x T
DP
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