Timers, Pulse timer – Rockwell Automation 1503VC IntelliVAC Plus Contactor Control Module User Manual
Page 138
DeviceLogix 9-15
1503-UM054C-EN-P – June 2013
Table 9.C – Bistable Function Block Output Table
Function
Reset
Input (Set) Output Value
at time = t
0
Output Value
at time = t
0+1
SR set dominant
(A set dominant block
goes to the set state if
both inputs are true.)
0
0
0
0
0
1
0
1
1
0
0
0
1
1
0
1
0
0
1
1
0
1
1
1
1
0
1
0
1
1
1
1
RS reset dominant
(A reset dominant block
goes to the false state if
both inputs are true.)
0
0
0
0
0
1
0
1
1
0
0
0
1
1
0
0
0
0
1
1
0
1
1
1
1
0
1
0
1
1
1
0
Timers
Timer function blocks control the state of a single output based on
the value of the accumulator and a Preset. They have two inputs
called input and reset which control the counting of the accumulator.
In the case of timers the accumulator accumulates time as opposed to
events such as a counter. The three timer blocks available are the
Pulse Timer, The On-Delay Timer and the Off-Delay Timer. All
three timers have a selectable time base of either 1 millisecond or 10
milliseconds. The timers are non-retentive. Only the output status is
available for use. No Timer Timing or Timer Done bits are
available. The different timers are described below.
Pulse Timer
The Pulse timer generates a TRUE value on its output for a fixed
amount of time. The duration of the TRUE pulse is determined by
the preset value along with the time base of the timer. When the
input to the timer changes from FALSE to TRUE, it sends the output
to TRUE and starts the accumulator counting. It then increments the
accumulator each time the time base number of milliseconds has
expired. When the accumulator reaches the preset value the timer
resets the output to FALSE.
In the pulse timer, the input acts only as a trigger to start the
accumulator counting. Once the accumulator starts timing, it
continues to rise regardless of the state of the input. As long as the
output is TRUE and the accumulator is counting, additional triggers
of the input do not affect the state of the output or the count of the
accumulator. Once the accumulator reaches the preset value and the