Rockwell Automation DEVICENET 1771-SDN, User Manual

Page: 131 / 139

Publication 1771-6.5.132 - June 2000
Data Map Example D-9
The following is an output data mapping scheme example for a
scanner in 1/2-slot addressing mode.
Module Status
55
15 0
79
95
125
N45
143
80
N1
word 0
word 1
word 2
word 3
word 4
word 5
word 6
word 7
word 8
In 1/2-slot addressing mode, 24 bits of the
output data table are used for the output
image table. The image table is for
discrete output bits. In the default mode,
the processor writes the output bits of the
first 24 nodes to the output image table via
DIO. The output bits from the remaining
nodes are written to the output data table.
Note that the output image table begins
with bit #16, where the output bit for node
#1 (MAC ID 1) is written. The output data
table now begins with bit #40, where the
output bit for node #25 (MAC ID 25) is
written.
The scanner takes the output bits from its
output data table and organizes them into
a strobe message. The strobe message
contains one bit for each node address,
0-63. In default mode, the scanner is node
0; therefore, this bit is empty. The scanner
sends a separate strobe message to each
network, via channel A and channel B.
Note: 1 word = 2 bytes
1 byte = 8 bits
Output Image Table
23 22 21 20 19 18 17 16
N1
(for discrete output data bits)
39 38 37 36 35 34 33 32
N23
31 30 29 28 27 26 25 24
16
N1
bit number
node number
N1 = node #1
40
N25
Output Data Strobe Message channel A
Output Data Strobe Message channel B
63 - - - - - - - - - - - - - - - - - - - - - - - - - 23 - - - - - - - - - - - - - - - 1 0
N23 N1
63 - - - - - - - - - - - 45 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1 0
N45
N1
Bit numbering in the data table is
right to left, beginning with zero.
Each node’s output bit is mapped to a bit number in the
strobe message that directly corresponds to that
particular node’s MAC ID. For example, the output bit
for node #23 is mapped to strobe bit #23.
Bit numbering in the data table is
right to left, beginning with zero.
Channel B
Channel A