Siemens SIMATIC S7-200 System Manual page 212

S7-200 Programmable Controller System Manual
Tip
To guarantee a minimum time interval, increase the preset value (PV) by 1. For example: To
ensure a minimum timed interval of at least 2100 ms for a 100-ms timer, set the PV to 22.
Table 6-74 Timer Numbers and Resolutions
Timer Type
TONR
( t (retentive) ti )
TON, TOF
( (non-retentive) t ti )
Understanding How Resolution Affects the Timer Action
For a timer with a resolution of 1 ms, the timer bit and the current value are updated asynchronous
to the scan cycle. For scans greater than 1 ms, the timer bit and the current value are updated
multiple times throughout the scan.
For a timer with a resolution of 10 ms, the timer bit and the current value are updated at the
beginning of each scan cycle. The timer bit and current value remain constant throughout the
scan, and the time intervals that accumulate during the scan are added to the current value at the
start of each scan.
For a timer with a resolution of 100 ms, the timer bit and current value are updated when the
instruction is executed; therefore, ensure that your program executes the instruction for a 100-ms
timer only once per scan cycle in order for the timer to maintain the correct timing.
Example: SIMATIC On-Delay Timer
Timing Diagram
198
Resolution Maximum Value
1 ms
10 ms
100 ms
1 ms
10 ms
100 ms
Network 1
LD
TON
Network 2
LD
=
I0.0
current = 10
T37 (current)
T37 (bit)
Q0.0
32.767 s (0.546 min.)
327.67 s (5.46 min.)
3276.7 s (54.6 min.)
32.767 s (0.546 min.)
327.67 s (5.46 min.)
3276.7 s (54.6 min.)
//100 ms timer T37 times out after
//(10 x 100 ms = 1s)
//I0.0 ON=T37 enabled,
//I0.0 OFF=disable and reset T37
I0.0
T37, +10
//T37 bit is controlled by timer T37
T37
Q0.0
1s
Timer Number
T0, T64
T1 to T4, T65 to T68
T5 to T31, T69 to T95
T32, T96
T33 to T36, T97 to T100
T37 to T63, T101 to T255
Maximum
value = 32767