4. Configuration
214
Figure 4-107. TOF_RET Block Graphic Behavior
Utilization example in ST language:
PROGRAM MainPrg
VAR RETAIN
bStart : BOOL := TRUE;
TOF_RET : TOF_RET;
END_VAR
// When bStart=FALSE starts counting
TOF_RET( IN := bStart,
PT := T#20S);
// Actions executed at the end of the counting
IF (TOF_RET.Q = FALSE) THEN
bStart := TRUE;
END_IF
TON_RET
The TON_RET implements a time delay to enable an output. When the input IN has its state changed
from FALSE to TRUE, or a rising edge, the specified time PT will be counted and the Q output will
be driven to TRUE at the end of it. When the input IN is in logic level 0 (FALSE), the output Q
remain in the same state (FALSE), even if it happens in the middle of the counting process. The PT
time can be changed during the counting as the block assumes the new value if the counting hasn’t
finished. Figure 4-108 depicts the TON_RET block and Figure 4-109 shows its graphic behavior.
Figure 4-108. TON_RET Function Block
This variable, when receives a rising edge,
enables the function block counting.
This variable specifies the block counting limit
(time delay).
Table 4-153. TON_RET Input Parameters
This variable executes a rising edge as the PT
variable (time delay) reaches its maximum
value.
This variable shows the current time delay.
Table 4-154. TON_RET Output Parameters
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