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User Data Areas for Allen-Bradley
Message areas
Table 15-3 indicates the number of message areas for event and alarm messages, the number of alarm message acknowledgement areas (PLC → Operating Unit and Operating Unit → PLC) and the total length of the respective
areas for the various operating units.
Table 15-3
Unit
Operating unit message areas
Event message area
Alarm messages area/
Alarm message area
Number Length (words)
Number Overall length per
per type type (words)
PC
8
125
8
125
OP37/Pro
8
125
8
125
MP270
8
125
8
125
The length of a contiguous area may not exceed 64 words.
Assignment of
message bit and
message number
A message can be configured for each bit in the message area. The bits are
assigned to the message numbers in ascending order.
Example:
The following event messages are configured for the PLC Allen-Bradley
SLC 500 / PLC-5:
N7
Element 8
Length 5 words
Figure 15-1 shows the assignment of all 80 (5 x 16) message numbers to the
individual bit numbers in the PLC event message area.
The assignment is performed automatically on the operating unit.
Figure 15-1
Assignment of message bit and message number
Communication for Windows-based Systems User’s Manual
Release 01/99
15-5