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Master Remote I/O Communications Section 4-1
4-1-3 Precautions on the Number of Master Units
The following system configurations can be constructed based on various
numbers of Master Units when DeviceNet Units are used.
Note Only one Master Unit can be connected to a network if the user specifies a
COS or cyclic connection from the Configurator. Remote I/O communications
errors may occur is more than one Master Unit is connected for a COS or
cyclic connection.
Max. No. of I/O
per Slave con-
trollable by a
DeviceNet Unit
Fixed allocations 2,048 pts (64 input words, 64 output words)
User-set
allocations
By allocated
DM Area
words
3,200 pts (100 input words, 100 output words)
By Configu-
rator
3,200 pts (100 input words, 100 output words)
Item Specifications
Pattern One Master Unit
connected on a single
network
Multiple Master Units connected
on a single network
Multiple Master Units connected
to a single PC
Configuration
Remote I/O communications
Fixed alloca-
tions
❍
×
❍
(Up to 3 Master Units can be
used.)
User-
set
alloca-
tions
By DM
Area
words
❍❍ (See note.) ❍
By
Config-
urator
❍❍ (See note.) ❍
Precautions Same as previous net-
works.
• The communications cycle time
is longer.
Note The communications cycle
time for the network in the
figure above is TA+TB if
sections A and B above are
separate networks with a
communications cycle time
of TA and TB.
• Multiple Master Units cannot
share a single Slave Unit.
• Bus Off errors (communications
stopped by multiple transmis-
sions) may occur if multiple
Master Units with disabled scan
lists are present on a single net-
work.
• The cycle time of the PC is long-
er.
• Make sure that each word allo-
cated in the system is allocated
to only one Master Unit.
Yes
AB