VIPA CPU 21 Series, Руководство пользователя

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Chapter 5 Deployment CPU 21x-2BT02 with H1 / TCP/IP Manual VIPA CPU 21x
5-4 HB103E - Rev. 05/45
H1 is a protocol that is based upon the Ethernet standard.
H1 information is exchanged between stations by means of H1-frames that
are transferred via transport connections.
A transport connection is a logical link between two access points to the
transport services on different stations. A transport connection is based
upon addressing information that provides an exact description of the path
between the two access points.
The following parameters describe a transport connection individually:
•
MAC address, also referred to as Ethernet address, gives an unique
definition of the access facility of a station.
•
TSAP Transport Service Access Points identify access channels for the
services of the transport protocol.
The CP prepares a data buffer and transfers the data into the data buffer
by means of the background communication function SEND_ALL. Then the
CP creates an H1-frame and transfers this to the partner station as soon as
this has enabled reception. When the partner station has received the H1-
frames, the CP receives an acknowledgment receipt. Next it uses the
background communication function RECEIVE_ALL to transfer the status
of the SEND-job into the respective indicator word.
This ensures error-free communications.
The following illustration shows the principle once again:
Send HTB
Data
Send_All
Status word
Data
Recv_All
H1-Frame
SEND job
Receive enable
H1-Frame
CPU CP
Receive ackn.
every frame
Reception terminated
H1-Bus
Daten
Status word
Recv-All
Receive job
CPU CP
H1-Frame
Data
Receive HTB
Recv_All
Reception terminated
Note!
Due to the large quantity of acknowledgment receipts that are transferred
via an H1 transport connection, the load on the network is appreciably
higher under H1 than under TCP/IP, however, under TCP/IP the security of
the data is reduced!
H1