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FX Series Programmable Controllers
Devices in Detail 4
4-24
4.11.2
Availability of High Speed Counters on 
FX
0
, FX
0S
 and FX
0N
 PLC’s
The following device table outlines the range of available high speed counters on both the FX
0
,
FX
0S
 and the FX
0N
Key:
U - up counter input 
D - down counter input
R - reset counter (input) 
S - start counter (input)
A - A phase counter input 
B - B phase counter input
- Counter is backed up /latched on both FX
0
, FX
0S
 and FX
0N
- Counter is backed up /latched on FX
0N
 only
  (FX
0
, FX
0S
 has no backup/latch on this device)
Input assignment:
Different types of counters can be used at the same time but their inputs must not coin-
cide. Inputs X0 to X3 cannot be used for more than one counter. For example, if C251 is 
used the following counters and instructions cannot be used; C235, C236, C241, C244, 
C247, C249, C252, C254, I0
, I1
.
Counter speeds and operational rules:
All inputs identified are 5 kHz inputs.
Only one 2 phase or A/B phase counter should be operated at any one time.
A  high speed counter specified in an applied instruction may not be modified by V or Z 
indexes.
Calculating the maximum combined counting speed on FX0S:
This is calculated as follows:(2 phase counter speed
 
x number of counted edges) 
 
(the sum of the speeds of the active 1 phase counters).
I
N
P
U
T
1 Phase counter
user start/reset
1 Phase counter
assigned
start/reset
2 Phase counter
bi-directional
A/B Phase counter
C235 C236 C237 C238 C241 C242 C244 C246 C247 C249 C251 C252 C254
X0
U/D
U/D
U/D
U
U
U
A
A
A
X1
U/D
R
R
D
D
D
B
B
B
X2
U/D
U/D
R
R
R
R
X3
U/D
R
S
S
S
Unit
type
Max. 1 phase
counting
speed
Sum of the
speeds of the
active 1 phase
counters
Max. 2 phase
counting
speed
Max. number of
2 phase
counters
Max. combined
sum of 1 and 2
phase counting
speeds
FX
0
,
FX
0N
5kHz
 5kHz
2 kHz
1
1 phase and 2
phase counters
cannot be mixed
FX
0S
7kHz
 14kHz
2 kHz
1
 14kHz see
note below
FX
0(S)
FX
0N
FX FX
(2C)
FX
2N(C)
C235
C236