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FX Series Programmable Controllers Devices in Detail 4
4-16
4.9.1 General timer operation
Timers operate b
y
countin
g
clock pulses (1, 10 and 100 msec). The timer output contact is
activated when the count data reaches the value set b
y
the constant K. The overall duration or
elapsed time, for a timers operation c
y
cle, is calculated b
y
multipl
y
in
g
the present value b
y
the
timer resolution, i.e.
A 10 msec timer with a present value of 567 has actuall
y
been operatin
g
for:
567
×
10 msec
567
×
0.01 sec = 5.67 seconds
Timers can either be set directl
y
b
y
usin
g
the constant K to specif
y
the maximum duration or
indirectl
y
b
y
usin
g
the data stored in a data re
g
ister (ex. D). For the indirect settin
g
, data
re
g
isters which are batter
y
backed/ latched are usuall
y
used; this ensures no loss of data
durin
g
power down situations. If however, the volta
g
e of the batter
y
used to perform the batter
y
backed service, reduces excessivel
y
, timer malfunctions ma
y
occur.
4.9.2 Selectable Timers
On certain pro
g
rammable controllers, drivin
g
a special auxiliar
y
coil redefines approximatel
y
half of the 100 msec timers as 10 msec resolution timers. The followin
g
PLC’s and timers are
sub
j
ect to this t
y
pe of selection.
-FX
0
, FX
0S
drivin
g
M8028 ON, timers T32 to 55 (24 points) are chan
g
ed to 10 msec
resolution.
-FX
0N
drivin
g
M8028 ON, timers T32 to 62 (31 points) are chan
g
ed to 10 msec resolution.
Driving special auxiliary coils:
• Please check the definition of special auxiliar
y
coils before usin
g
them.
Not all PLC’s associate the same action to the same device.