Rockwell Automation 2711 PanelView 550/900 Profibus Communications User Guide - Manual (Page 21)

PROFIBUS DP Communications 21
Publication 2711-6.3
Multiplex Handshake Error Processing
When the PanelView receives a new command word from the DP
Master (handshake bit is set to 1) it verifies that the Block Out and
Block In numbers have been allocated in the PanelView terminal’s
database.
•
If the Block Out number is invalid, the PanelView will set the
Block Out number of the status word to 0 and ignore the data sent
by the DP Master in the multiplex output module.
•
If the Block In number is invalid, the PanelView will set the
Block In number of the status word to 0 and set all of the data in
the multiplex module to 0. The DP Master should then ignore the
data.
In either case, the following occurs:
•
the PanelView sets the status word’s handshake bit to 1 to
acknowledge the DP Master request.
•
the corresponding extended diagnostic bytes are generated (see
page 35.
We recommend that your DP Master program verify that the block
numbers received in the status word match the block numbers sent in
the control word. If they do not match, the master program should
execute an error processing routine.