Rockwell Automation 1395 Node Adapter Board - Manual (Page 20)

Chapter 3
Functional Description
3-8
The first 3 bits of the Logic Command word (Parameter 150 in this
example), are used to determine which speed reference will be used by the
drive. If the normal run speed reference input to Parameter 154 is to be
used, all three bits must be 0. If a preset speed or the MOP function will be
used, bits 0–2 are set accordingly (refer to the Bulletin 1395 Installation
and Maintenance manual for a complete description of the Logic
Command bits). In this example, the first three bits of word 2 of integer file
N7 are used to determine the speed reference used by the drive as shown
on rung 4 in Figure 3.3.
If the normal run speed reference is selected, the PLC Controller must send
a 16 bit word to External Vel Ref (Parameter 154) in the drive. Because the
speed reference is a complete 16 bit word, the PLC Controller must send
the data as a complete word rather than as individual bits as was the case
for logic command bits. In this example, word 1 of integer file N10 is used
to store the speed reference for the drive. The MOV block in rung 6 of
Figure 3.3 transfers the 16 bit word of N10:01 to word 2 of the output
image table. Because word 2 of the output image table is sent to Parameter
301, which in turn is linked to Parameter 154 (Figure 3.2), the 16 bit word
N10:01 is the speed reference input to the drive Parameter 154.
Information transferred back to the PLC Controller from the drive is
handled much as it was in the previous example, with the exception that
data is transferred from the input image table of the PLC Controller to the
working data files in the PLC Controller program. Again, note that bit
coded words such as Logic Status (Parameter 100), are bit numbered in
octal in the PLC Controller, while the drive is in decimal.
Block Transfer In addition to using the I/O image table to transfer data to the drive on a
continuously updated basis, there are some conditions where data must be
transferred on an occasional basis only or in large blocks of data. To
perform this, the Node Adapter Board allows for use of the PLC Controller
block transfer function. The block transfer function does not directly use
any of the discrete I/O slots in the rack. However, the Node Adapter Board
requires the use of several bits in the PLC Controller input image table to
transfer a Node Adapter status byte. The status information must be
updated at the same rate as the standard I/O, therefore, the Node Adapter
Board reserves the first group in the rack for the Node Adapter status byte
(see Figure 3.1). The PLC Controller does not send status information to
the Node Adapter Board for the block transfer. As a result, the 16 bits
associated with the first group in the PLC Controller output image table are
not used.