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KEEP(011) operates like the self-maintaining bit described in 4-7-4 Self-main-
taining Bits (Seal). The following two diagrams would function identically, though
the one using KEEP(011) requires one less instruction to program and would
maintain status even in an interlocked program section.
00000
LD
000002
00001
OR
000500
00002
AND NOT
000003
00003
OUT
000500
00000
LD
000002
00001
LD
000003
00002
KEEP(011)
000500
S
R
Address
Instruction Operands
Address
Instruction Operands
0005
00
0000
02
0005
00
0000
03
0000
02
(011)
KEEP 000500
0000
03
Example
KEEP(011) can be used to create flip-flops as shown below.
0000
(011)
KEEP 000001
0000
00
00
0000
01
0000
01
↑
↑
000000
000001
00000
LD
"
000000
00001
AND NOT
000001
00002
LD
"
000000
00003
AND
000001
00004
KEEP(011)
000001
Address
Instruction Operands
Note: Immediate-refresh variations can be used in simplex mode only; they cannot be
used in duplex mode.
Precautions
Any output bit is generally used in only one instruction that controls its status.
Never use an input bit in a normally closed condition on the reset (R) for
KEEP(011) when the input device uses an AC power supply. The delay in shut-
ting down the PC’s DC power supply (relative to the AC power supply to the input
device) can cause the operand bit of KEEP(011) to be reset. This situation is
shown below.
Input Unit
A
NEVER
S
(011)
[ KEEP
120000 ]
R
A
Bits used in KEEP are not reset in interlocks. Refer to the 5-8 INTERLOCK and
INTERLOCK CLEAR: IL(002) and ILC(003) for details.
Note: Refer to page 101 for general precautions on operand data areas.
Flags
There are no flags affected by this instruction.
Bit Control Instructions
Section 5-7
Summary of Contents for CVM1D
Page 462: ...SYSMAC CVM1D Duplex System Programmable Controllers Operation Manual Revised August 2001...
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