Parker Hannifin S.p.A. - Divisione S.B.C. LVD User’s Manual
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3.17 Other useful functions
Table function
The LVD drive features a table composed of 64 (256) elements that can be used for a wide
range of functions, including:
- storage of alternative values for basic parameters
- storage of up to 64 positionings
- generation of complex speed or position profiles
- generation of electronic cams (see operating mode 15)
The table is administrated by means of parameters Pr43 and Pr44; Pr43 is the stack pointer
while Pr44 shows the value of the currently selected element.
Valid values for Pr43 are from 0 to 255 corresponding to the 256 elements of which only
the first 64 can be retained in the memory while the elements from 64 to 255 are reset each
time the drive is powered up.
There is a parameter designated Pr44+1 which is not accessible from the keypad and which
assumes the value of the successive element after the element selected by Pr43; this function
is invaluable when the table is organised in long format.
The LVD drive handles the table every 6.144ms as follows: if the Pr44 value is changed or
both Pr43 and Pr44 are changed, the LVD stores the value of Pr44 in the location pointed by
Pr43; if Pr43 is changed the LVD shows the pointed value in Pr44. When Pr43 is changed
Pr44 is updated in the next scan of pico-PLC; if pico-PLC has to write a table value, first set
Pr43 and then Pr44, only one change is allowed in the same scan cycle.
In the same way in order to read a table value via serial link, it is necessary to set Pr43 and
after 6.144ms it is possible to read Pr44 value; to write a table value via serial link, it is
necessary to set Pr43 and Pr44, waiting for 6.144ms before reading or writing another value.
If the table function is not utilised, Pr43 can be used as a general purpose parameter.
In the pico-plc programme the parameters from 128 to 255 correspond to the first 128
parameters of the table. Note that Pr43, Pr44 have the priority, so set Pr43 with a value higher
then 128 to avoid overwrite if you access directly to the table from the plc programme.
Quote compare functions
Parameters Pr96:95 and Pr98:97 have an alternative role as quote compare functions.
With b94.10 = 0, b94.8 = 1 if Pr96:95 > Pr63:62
With b94.10 = 1, b94.8 = 1 if Pr96:95 > Pr61:60
With b94.11 = 0, b94.9 = 1 if Pr98:97 > Pr63:62
With b94.11 = 1, b94.9 = 1 if Pr98:97 > Pr61:60
This function is performed every 6.144 ms.
If the quote compare functions are not utilised, parameters Pr95, Pr96, Pr97, Pr98, b94.10
and b94.11 can be used by the PLC program as general purpose registers.
Dimension capture
At each positive front of digital input 2 the value of Pr63:62 is captured and deposited in
Pr49:48 and b94.15 is set to 1 to signal the event. Instead of being automatic, b94.15 is reset
by means of the Pico PLC or the serial line.