Rockwell Automation 57C570 AutoMax PC3000 User Manual - Manual (Page 189)

18Ć7
Registers Description
Register 19 Ć
Messages
Transmitted
This register reflects the total number of messages
transmitted by the module. While the line is inactive, this
value will remain unchanged in the slave. In the master,
this value will rapidly increase as initialization request
messages are constantly being sent. While the line is
active, this value will constantly increase to 65535 and
then roll over to zero.
Register 20
(Drop Depth)
In the master, this register is not used. In the slave, this
register is used to define the number of drops that
particular slave module represents. The drop depth
register must never be set to a value less than 1 or greater
than 56 minus the drop setting. In other words, if the drop
setting is 54, the drop depth cannot be set greater than 2.
Likewise, if the drop setting is 10, the drop depth cannot
be set greater than 46.
The drop depth should be set to the minimum value
required to satisfy the application to minimize the update
period for that module. The drop depth value can be
modified at any time without removing an active drop from
the network. Note that the assignment of physical or
virtual drops must not overlap or transmission collisions
will occur.
Bit 14 of this register is the error bit. It is set by the
Network module if the existing drop depth value is invalid.
When bit 14 is set, the last valid drop depth value is used.
An invalid drop depth value written by an application task
should be discovered and corrected during initial system
testing.
Bit 15 is the processing complete bit. It is set when the
Network module has completed processing of the drop
depth register. If the drop depth value is changed by an
application task, the task must monitor bit 15 to verify that
the drop depth value processing has been completed by
the Network module.
To assign drop depth, an application task writes the
desired integer value to this register. The processing
complete bit (bit 15) and the error bit (bit 14) should then
be monitored to verify that the drop depth value has been
accepted and processed. The application task must
ensure that the processing complete bit is equal to 1 and
the error bit is equal to 0 before proceeding.