
79
Input Unit
A
NEVER
S
R
KEEP(12)
DR 03
A
Bits used in KEEP are not reset in interlocks. Refer to the 3-7-10 INTER-
LOCK and INTERLOCK CLEAR - IL(02) and ILC(03) for details.
If a DR bit is used, bit status will be retained even during a power interrup-
tion. KEEP(12) can thus be used to program bits that will maintain status af-
ter restarting the PC following a power interruption. An example of this that
can be used to produce a warning display following a system shutdown for
an emergency situation is shown below. Bits 0002, 0003, and 0004 would be
turned ON to indicate some type of error. Bit 0001 would be turned ON to
reset the warning display. DR 0000, which is turned ON when any one of the
three bits indicates an emergency situation, is used to turn ON the warning
indicator through 0100.
DR 0000
0100
0002
0003
0004
0001
Reset input
Indicates
emergency
situation
Activates
warning
display
Address
Instruction
Operands
000
LD
0002
001
OR
0003
002
OR
0004
003
LD
0001
004
KEEP(12)
DR
0000
005
LD
DR
0000
006
OUT
0100
S
R
KEEP(12)
DR 0000
KEEP(12) can also be combined with TIM to produce delays in turning bits
ON and OFF. Refer to 3-7-14 TIMER - TIM for details.
3-7-10
INTERLOCK and INTERLOCK CLEAR - IL(02) and ILC(03)
Ladder Symbol
IL(02)
Ladder Symbol
ILC(03)
IL(02) is always used in conjunction with ILC(03) to create interlocks. Inter-
locks are used to create program sections that are either executed normally
or partially reset and frozen, depending on the interlock condition (i.e., the
execution condition of IL(02)). If the execution condition of IL(02) is ON, the
program will be executed as written.
If the execution condition for IL(02) is OFF, the interlocked section between
IL(02) and ILC(03) will be treated as shown in the following table:
Example
Description
Instruction Set
Section 3-7