ACC-72EX User Manual
DPRAM Data Processing
67
Note
In case of a network fault (e.g. disconnected network cable), a slave
firmware keeps the last state of the input data image. As soon as the
firmware detects the network fault, it clears the Communicating flag
in the netX communication flags. The input data should then no longer
be evaluated.
Start / Stop Communication
Controlled or Automatic Start
The firmware has the option to start network communication after power up automatically. Whether or
not the network communication will be started automatically is configurable. However, the preferred
option is called “Controlled Start of Communication.” This option forces the channel firmware to wait for
the host application to allow network connection being opened by setting the Bus On flag in the
Application Change of State register in the channel’s control block. Consequently, the protocol stack will
not allow the opening of network connections and does not exchange any cyclic process data until the Bus
On flag is set.
The second option enables the channel firmware to open network connections automatically without
interacting with the host application. It is called “Automatic Start of Communication.” This method is
not recommended because the host application has no control over the network connection status. In this
case, the Bus On flag is not evaluated.
Note
The Controlled Start of communication is the default method used for
the default dual-port memory layout.
Start / Stop Communication through Dual-Port Memory
(Re-)Start Communication
To allow the protocol stack to open connections or to allow connections to be opened, the application sets
the Bus On flag in the Application Change of State register in the channel’s control block. When
firmware has established a cyclic connection to at least one network mode, the channel firmware sets the
Communicating flag in the netX Communication Flags register.
Stop Communication
To force the channel firmware to disable all network connections, the host application clears the Bus On
flag in the “Application Change of State” register in the channel’s control block. The firmware then
closes all open network connections. A slave protocol stack would reject attempts to reopen a connection
until the application allows opening network connections again (Bus On flag is set). When all
connections are closed, the channel firmware clears the Communicating flag in the netX Communication
Flags register.
