Handshake Method - Panasonic FP2 ET-LAN Technical Manual

4.4 Handshake Method

4.4.1 Handshake Method
Handshake method
The CPU unit and ET-LAN unit carry out initialization and termination processing, open and close
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processing, various types of communication processing requests, and confirmation of completion by
means of a handshake.
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.
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Handshakes using the I/O and using the shared memory
Item
Operation The various processes are executed
method by reading from and writing to the
input contacts X and output contacts Y
allocated to the ET-LAN unit from the
ladder program.
Programming The input contacts X and output
cautions contacts Y can be used as it is.
Operation in The output contacts Y all go off. At
PROG. mode 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.
Limits on the For MEWTOCOL communication, all
communicatio processes can be realized using
n functions connections 1 to 8.
that can be For transparent communication, only
used the processes for connections 1 to 3
can be realized. I/O handshaking
cannot be realized.
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.
Input conditions such as complete signals and error signals are updated in both the input relay <I/O>
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and the complete signal area <shared memory>.
Output conditions such as request signals operate under the logical OR of the output relay <I/O> and
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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.
4-8
I/O handshaking Shared memory handshaking
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.
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.
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.
For both MEWTOCOL communication and
transparent communication, all processes
can be realized using connections 1 to 8.