Panasonic FP2 ET-LAN, Technical Manual

Page: 44 / 306

4-8
4.4 Handshake Method
4.4.1 Handshake Method
Handshake method
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The CPU unit and ET-LAN unit carry out initialization and termination processing, open and close
processing, various types of communication processing requests, and confirmation of completion by
means of a handshake.
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There are two types of handshake, one using the I/O and one using the shared memory.
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Both types can be used at the same time.
Handshakes using the I/O and using the shared memory
Item I/O handshaking Shared memory handshaking
Operation
method The various processes are executed
by reading from and writing to the
input contacts X and output contacts Y
allocated to the ET-LAN unit from the
ladder program. The various processes are executed by
reading from and writing to the handshaking
area allocated to the shared memory in the
ET-LAN unit from the ladder program.
Programming
cautions The input contacts X and output
contacts Y can be used as it is. The F150 (READ)/PREAD (P150), F151
(WRT)/P151 (PWRT) instructions are used
to reflect the content of the shared memory
handshake area to internal relays etc.
Operation in
PROG. mode The output contacts Y all go off. At
this time, all connections
(communication routes) are closed
forcibly (communication not possible).
Therefore, if the CPU unit switches
from RUN to PROG. mode due to
some error occurring, communication
stops. As the shared memory is not changed even
in PROG. mode, the connection
(communication route) is not closed.
However, if the connection is closed from
another node when in PROG. mode, the
ET-LAN will not execute a process to
reopen it. When you switch from PROG.
mode to RUN mode, and the reinitialize and
re-opening processes are not executed, we
recommend that you construct a program
after referring to the flow chart on page 4-
16.
Limits on the
communicatio
n functions
that can be
used For MEWTOCOL communication, all
processes can be realized using
connections 1 to 8.
For transparent communication, only
the processes for connections 1 to 3
can be realized. I/O handshaking
cannot be realized. For both MEWTOCOL communication and
transparent communication, all processes
can be realized using connections 1 to 8.
I/O handshaking and shared memory handshaking can be used simultaneously.
Note:
If both the I/O and shared memory handshakes are used at the same time, operation is as follows.
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Input conditions such as complete signals and error signals are updated in both the input relay <I/O>
and the complete signal area <shared memory>.
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Output conditions such as request signals operate under the logical OR of the output relay <I/O> and
the request signal area <shared memory>. As a result, if both are on, the result is on, and an off result
is produced only if both are off.