Isochronous Mode - Siemens SIMATIC S7-300 Manual

3.10 Digital input module SM 321; DI 16 x 24 VDC; with hardware and diagnostic interrupts (6ES7321-7BH01-0AB0)
Technical data
Input current
with "1" signal
•
Input characteristics
Connection of 2-wire BEROs
Permissible quiescent current
•
Wiring signal transducers
Shunt circuit of the encoder, for wire-break detection
Time/frequency
Internal preparation time for status processing (non-synchronous
operation)
Enable hardware and diagnostics interrupt
•
Input delay
programmable
•
Rated value
•
3.10.1

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.)
Requirements
● The DP master and slave must support isochronous mode. STEP 7 V5.2 or higher.
S7-300 Automation System Module data
Manual, 08/2006, A5E00105505-04
typ. 7 mA
to IEC 61131, type 2
supported
max. 2 mA
with 20-pin front connector
10 kohms to 18 kohms
max. 40 ms
Yes
typ. 0.1/0.5/3/15/20 ms
Digital modules
3-25