Omron CQM1-ARM21, Руководство по эксплуатации

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Introduction
Section 1-1
4
No termination
The network topology may be a star, a line with or without branch lines, or a
full tree structure. Termination is not required.
star line branch lines
tree
controller
Master
controller
Master
Master
Master
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
controller controller
The maximum cable length for the total system may not exceed 100 m. By
using 2 repeaters and additional AS-Interface power supplies, this can be
extended to up to 300 m.
1-1-3 Technical Details
This section will provide some technical details of the AS-Interface system. It
is not essential to understand all details in order to operate the CQM1-
ARM21.
Concept The aim of AS-Interface is to supply energy to, AND exchange I/O data with
slave stations over a simple unshielded two-wire cable. To achieve this, while
maintaining reliability and electromagnetic compatibility in an industrial
environment, a specific communication model has been developed which
ensures encoding without a DC signal component and a very narrow power
spectrum.
•
Messages are encoded in Manchester II format.
•
Modulation is by alternate pulse modulation (APM).
•
The transmitter, in both master and slave, acts as a current sink
generating sine-shaped pulses.
•
The characteristic impedance of the power supply unit transforms each
current pulse into a sin²-shaped voltage pulse.
•
One bit time (T
Bit
) is defined as 6
µ
s, resulting in a bit sequence frequency
of 166.67 kbit/s.
Communication principles All communication on the AS-Interface line is controlled by the master. The
AS-Interface specification prescribes in detail which sequence of actions the
master must follow. On the highest level, the execution control is managed as
shown below: