Rockwell Automation D17846.2.4 CONTROLNET KT EMULA - Manual (Page 22)

Publication 1784-6.2.4 - September 1997
3-2 How Your Driver Operates the KTCX Card
Typical Communications Methodology
To send data you must:
• Build the data packet.
• Send the data packet.
• If expecting a reply, follow the receive data methodology when
the reply arrives.
To receive data you must:
• Receive an interrupt from the KTCX card if using interrupts, or
monitor receive mailboxes if not.
• Copy the packet from the Receive Mailbox.
• Return the application to the mainstream.
Solicited Messaging
In the case of solicited messaging where the card behaves as a client,
all messages are transmitted to the destination.
Unsolicited Messaging
The card supports unsolicited messaging from devices like the
PLC5-C and KFC operator interfaces.
Multi-Message Queuing
The application that keeps track of the transaction numbers (TNS)
must handle multi-message queuing. It must associate the order of in-
coming and out-going message packets. The receiving node always
returns the TNS unchanged. Always keep the same TNS when
responding to a remote request, otherwise the remote sender will not
recognize the packet is associated with the original request.
Send and Receive
Overview Use the following procedures to send and receive messages and
commands.
Operating the Send and Receive Flags
Two flags—Access Request and Data Valid—control each send and
receive mailbox. When sending commands or messages, use the Send
Access Request flag (byte 0080h) and the Send Data Valid flag (byte
0081h). When receiving commands or messages, use the Receive
Access Request flag (byte 0480h) and the Receive Data Valid flag
(byte 0481h).
The host and the KTCX card transfer control of these bytes during
each transmission. When both these bytes are set to 00h, the KT card
has control of the mailbox. When both of these bytes are set to 01h,
then the host has control of the mailbox.