Rockwell Automation 2711 PanelView 550/900 Profibus Communications User Guide - Manual (Page 18)

PROFIBUS DP Communications 18
Publication 2711-6.3
The following outlines the steps required to initiate and complete a
multiplex module data exchange from the DP Master.
DP Master:
•
Before initiating the exchange, both the control word and status
word handshake bits must be 0.
•
If multiplex output data is being sent to the PanelView terminal,
the multiplex output block’s data must be copied into the
multiplex output module’s data area in the DP Master database
(starting at word 1).
•
The multiplex output block number must be placed in the
multiplex output module’s control word (the Block Out field).
•
If multiplex input data is being requested from the PanelView
terminal, the multiplex input block number must be placed in the
multiplex output module’s control word (the Block In field).
•
The exchange is initiated by setting the handshake bit in the
control word to 1.
PanelView:
•
When the PanelView terminal detects the handshake bit in the
control word is set, any further processing is based on the value
of the Block Out or Block In fields. If the Block Out number is
non–zero, it will copy the multiplex output module data into the
corresponding multiplex output block in the PanelView’s
database. If the Block In number is non–zero, then it will copy a
multiplex input block from its database into the multiplex input
module. The status word’s handshake bit is set to 1 to indicate to
the DP Master that the PanelView processing is complete.
DP Master:
•
The handshake bit in the status word is monitored until a 1 is
detected. If a multiplex input block was requested it may then be
extracted from the multiplex input module and copied into the DP
Master’s database. Also, any error checking of the status word’s
Block In or Block Out fields must take place at this time.
•
The DP Master acknowledges completion of the exchange by
setting the handshake bit in the control word to 0.
PanelView:
•
When the PanelView detects the DP Master has cleared the
handshake bit in the control word, the PanelView acknowledges
completion of the exchange by clearing the handshake bit in the
status word to 0.
DP Master:
•
The handshake bit in the status word is monitored until a 0 is
detected. Then the DP Master may initiate another multiplex
module data exchange.
Note: Only one multiplex module data exchange operation can be in
progress at any one time.