Rockwell Automation 1395 Multi-Comm Hardware/Software - Manual (Page 38)

Chapter 3
Configuration & Interfacing
3–27
Group: – The group number of the first in the group in the rack as
specified above. If the Drive is setup as a 3/4 rack, the first group could be
0 or 2. If the Drive has been setup as a full rack, group number is 0. If the
Drive is setup as a half rack, the first group number could be 0 or 4. Refer
to Figures 3–9 through 3–11 for details.
Module: – The module number associated with the block transfer function
in the first group. This is always set to 0.
Control Block: – A set of words which contain information about the PLC
Controller block transfer instruction. In PLC–5 Controllers, the Control
Block requires 5 contiguous words. In Figure 3–18, words N111:0 through
N111:4 have been reserved for BTW information and words N111:90
through N111:94 have been reserved for the BTR information.
Data File: – The actual block transfer message to be sent to the Drive. It
contains the message header and any data to be sent with the message. The
number of words required for the data portion is dependent on the message
being sent. Refer to the message format section of this manual for details.
In Figure 3–18, N111:5 is the first word in the data file for the BTW
instruction and N111:50 is the first word in the file for the BTR instruction.
Length: – Specifies the total length of the block transfer message in words.
The BTR length value must be a minimum of 40 words regardless of the
BTW length value. The Drive always returns at least 40 words with each
message.
IMPORTANT: The low byte of word 4 in the block transfer message
header contains the length of the message in bytes. The only difference
between the length value in the message header and the length value in the
block transfer instruction is the units used to specify them. In Figure 3–18,
the length is 6 words for BTW, which will appear as 12 bytes (6 words), in
word 4, low byte of the message header. For the BTR, the length value of
the header message should be the length in bytes of the actual message.
regardless of the length of 40 in the Block transfer instruction.
Continuous: – Specifies whether the block transfer instruction is executed
on a continuous basis or only when enabled by the program. Normally,
because of the nature of data being transferred to the Drive, this is set to
“N”, representing non-continuous execution.