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Assigning System Devices 9
9-1
9. Assigning System Devices
9.1 Addressing Extension Modules
Most of the FX famil
y
of PLC’s have the abilit
y
to connect additional discreet I/O and/or special
function modules. To benefit from these additional units the user must address each block
independentl
y
.
Addressing Additional Discrete I/O
This t
y
pe of I/O is the standard
input and output modules. As each
extension block or powered
extension unit is added to the
s
y
stem the
y
assume the next
available ad-dresses. Hence, the
units closest to the base unit will
have the lowest I/O numbers or
addresses. I/O numbers are
alwa
y
s counted in octal. This
means from 0 to 7 and 10 to 17
etc. Within a users pro
g
ram the
additional addresses are used as
normal. Discreet I/O can be added
at the users discretion as lon
g
as
the rules of s
y
stem confi
g
uration for each PLC t
y
pe are obe
y
ed. This information can be found
in the appropriate hardware manual.
For eas
y
use and identification, each additional I/O unit should be labeled with the appropriate
I/O numbers usin
g
the provided number labels.
Caution when using an FX system with FX-8ER, FX-24MR units
• When an FX-8ER or an FX-24MR are used an additional 8 points (as 4 inputs, 4 outputs)
of I/O must be allowed for. This is because both units split blocks of 8 inputs and 8
outputs to obtain a ph
y
sical 4 input/ 4 output confi
g
uration. Hence, an FX-8ER unit
actuall
y
occupies 8 input points and 8 output points even thou
g
h there are onl
y
4
ph
y
sical inputs and 4 ph
y
sical outputs.
Addressing Special Function Blocks
Special function blocks are allocated a lo
g
ical ‘station/block number’ from 0 to 7. This is used
b
y
the FROM/TO instructions to directl
y
access each independent special function module.
The lower the ‘station/block number’ is, the closer to the base unit it can be found. Special
function blocks can be added at the users discretion but the rules of confi
g
uration for each t
y
pe
of PLC must be obe
y
ed at all times. The confi
g
uration notes can be found in the appropriate
hardware manual for each pro
g
rammable controller.
POWER
FX-16EX
POWER
FX-8EX
POWER
FX-8EYT
POWER
FX-8EYR
FX-48MR
X0-27
X30-X37 X40-X57 X60-X67
Y0-Y27
Y30-Y37 Y40-Y47
FX Series Programmable Controllers