22
To designate a drive parameter as mirrored, simply enter its Modbus holding
register number into
Ext Comm Cfg #5
∼
Ext Comm Cfg #8
. The factory
default values of parameters
Ext Comm Cfg #5
∼
Ext Comm Cfg #8
are
0, which means “not designated”. As an example, let’s say that our application
requires that we constantly be monitoring ASD parameters “output voltage”
(FE05) and “status 2” (FE41). To mirror these parameters, we would first
convert their parameter numbers to decimal to determine the holding register
numbers (FE05
16
= 65029
10
and FE41
16
= 65089
10
), and then enter these
decimal numbers into two of the
Ext Comm Cfg
parameters. In this case, we
can enter a value of 65029 into parameter
Ext Comm Cfg #5
and a value of
65089 into
Ext Comm Cfg #6
. Upon completing this (and cycling power to
the drive), ASD parameters FE05 and FE41 will now be mirrored. This means
that network accesses to Modbus holding registers 65029 and 65089 (and
3589 and 3649 by virtue of register remapping as detailed in section 8.5) will
now be faster than if these registers were not being mirrored.
There are several issues to note regarding data mirroring:
•
ASD parameters that are being mirrored do not have any data
checking processing available. Therefore, a Modbus “success
response” will be returned to the network master even if the written
data value was invalid (out of range, for example). Therefore, use
caution with values written to command-type registers that are being
mirrored. In all cases, a mirrored register will return its current value
when read, so a write confirmation can be performed by reading a
command register after a write, and confirming that the read value
equals the previously-written value.
•
When entering “upper address” range parameter numbers (i.e.
parameters with indexes of FA00 - FFFF) into
Ext Comm Cfg #5
∼
Ext Comm Cfg #8
, either the “actual” (Fxxx) or remapped (0xxx)
parameter number may be entered with equal results. Using our
previous example of mirroring ASD parameters FE05 and FE41 as a
demonstration of this, we could have entered either 65029 or 3589
into
Ext Comm Cfg #5
, and either 65089 or 3649 into
Ext Comm
Cfg #6
and obtained the same results (“output voltage” and “status
2” would be mirrored).
•
Ext Comm Cfg #5
∼
Ext Comm Cfg #8
do not need to be used in
any particular order. For example, if only one user-defined parameter
was to be mirrored, its parameter number could be entered into any of
the
Ext Comm Cfg #5
∼
#8
parameters with equal results.
•
Recall from the discussion regarding parameter
Ext Comm Cfg #3
in section 7.1 that if a timeout time is selected and a timeout event
occurs, then all user-selectable mirrored command registers (i.e.
those registers that affect drive control or configuration) will be
automatically written with a “failsafe” value of 0. Refer to section 8.8
for more information.
•
The use of user-selectable mirroring is entirely optional, and therefore
is not required for proper network and drive operation, nor does it
Buy: www.ValinOnline.com | Phone 844-385-3099 | Email: [email protected]
