Programming instructions

76
Presets
Preset is the length of time the timer runs before finishing. The preset indicates
units of time bases. Thus T0 with a value of 50 runs for 5 seconds (50 x .1
seconds = 5 sec).
The preset must be a number between 1 and 32,767, because timers are 16 bit
registers.
Timer presets can be either a K constant, or a variable, such as a data register.
Having a D device as the preset allows an operator to make changes to the
timing duration from an HMI, or allows the program to change the preset based
on the ladder logic.
Timers only time up.
Reset (Retentive)
The accumulated value of a timer returns to 0 when the input conditions of the
timer rung become false. This is not the case with retentive timers. To return a
retentive timer accumulated value to 0 it is necessary to use the RST T#
instruction.
Non-retentive timers will lose their accumulated values at power down unless
they have been declared battery-back in PLC parameters.
12.2 Counters
Availability
FX2N, FX2NC, and FX3U PLCs have 256 counters.
FX1N PLC has 256 counters.
FX1S PLCs have 45 counters.
PLC Counter Address
Counter Type FX1S FX1N FX2N/FX2NC/FX3U
16-Bit 0-15 0-15 0-99
16-Bit Latched 16-31 16-199 100-199
32-Bit Bi-directional - 200-219 200-219
32-Bit Bi-directional Latched - 220-234 220-234
High Speed Counters 235-254 235-255 235-255
Note: Although counters C235 to C255 (21 points) are all high speed counters,
they share the same range of high speed inputs. Therefore, if an input is
already being used by a high speed counter, it cannot be used for any
other high speed counters.
Note: FX1S does not have C239, C240, C243, C245, C248, C250, or C253.