Table of Contents
Advertisement
Chapter 4. Ladder Diagram (LD) Programming
Timing diagram
ENABLE
Q
A
B
A. ENABLE and Q both go high; timer is reset (CV = 0).
B. ENABLE goes low; timer starts accumulating time.
C. CV reaches PV; Q goes low and timer stops accumulating time.
D. ENABLE goes high; timer is reset (CV = 0).
E. ENABLE goes low; timer starts accumulating time.
F. ENABLE goes high; timer is reset (CV = 0) before CV had a chance to reach PV. (The diagram is
not to scale.)
G. ENABLE goes low; timer begins accumulating time.
H. CV reaches PV; Q goes low and timer stops accumulating time.
Operands for OFDT
Parameter Description
Address
The beginning address of a three-word WORD array:
(????)
Word 1: Current value (CV)
Word 2: Preset value (PV)
Word 3: Control word
PV
The Preset Value, used when the timer is enabled or reset.
0 PV +32,767. If PV is out of range, it has no effect on Word 2.
CV
The current value of the timer.
Example for OFDT
The output action is reversed by the use of a negated output
coil. In this circuit, the OFDT timer turns off negated output coil
%Q0001 whenever contact %I0001 is closed. After %I0001
opens, %Q0001 stays off for 2 seconds then turns on.
222
PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual
C
D
E
Do not use the Address, Address+1, or Address+2
addresses with other instructions. Overlapping
references cause erratic timer operation.
F G
H
Warning
Allowed Operands Optional
R, W, P, L, symbolic
No
All except S, SA, SB,
Optional
SC
All except S, SA, SB,
Optional
SC, constant
GFK-2950C
Advertisement
Table of Contents
