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4-7-1 DIFFERENTIATE UP and DIFFERENTIATE DOWN
DIFFERENTIATE UP and DIFFERENTIATE DOWN instructions are used to
turn the operand bit ON for one scan at a time. The DIFFERENTIATE UP instruc-
tion turns ON the operand bit for one scan after the execution condition for it
goes from OFF to ON; the DIFFERENTIATE DOWN instruction turns ON the op-
erand bit for one scan after the execution condition for it goes from ON to OFF.
Both of these instructions require only one line of mnemonic code.
Address Instruction
00000 LD 000000
00001 DIFU(013) 000200
Operands
00002 LD 000001
00003 DIFD(014) 000200
(013)
DIFU 000200
(014)
DIFD 000200
0000
00
0000
01
Here, CIO 000200 will be turned ON for one scan after CIO 000000 goes ON.
The next time DIFU(013) 000200 is executed, CIO 000200 will be turned OFF,
regardless of the status of CIO 000000. With the DIFFERENTIATE DOWN
instruction, CIO 000200 will be turned ON for one scan after CIO 000001 goes
OFF (CIO 000200 will be kept OFF until then), and will be turned OFF the next
time DIFD(014) 000200 is executed.
Note Version-2 CVM1 CPUs also provide UP(018) and DOWN(019) that can be used
to differentiate changes in the execution condition to control execution. Refer to
Section 5 Instruction Set
for details.
4-7-2 SET and RESET
SET and RESET instructions are used to control the status of the operand bit
while the execution condition for them is ON. When the execution condition is
OFF, the status of the operand bit will not be changed.
(015)
SET 000200
00000
00
00000 LD 000000
00001 SET(015) 000200
00002 LD 000001
00003 RSET(016) 000201
Address Instruction Operands
(016)
RSET 000201
00000
01
In the above example, CIO 000200 will be turned ON when CIO 000000 goes
ON and will remain ON even after CIO 00000 goes OFF unless turned OFF
somewhere else in the program. CIO 000201 will be turned OFF when
CIO 000001 goes ON and will remain OFF even after CIO 00000 goes OFF un-
less turned ON somewhere else in the program.
4-7-3 KEEP
The KEEP instruction is used to maintain the status of the operand bit based on
two execution conditions. To do this, the KEEP instruction is connected to two
instruction lines. When the execution condition at the end of the first instruction
line is ON, the operand bit of the KEEP instruction is turned ON. When the
execution condition at the end of the second instruction line is ON, the operand
bit of the KEEP instruction is turned OFF. The operand bit for the KEEP instruc-
tion will maintain its ON or OFF status even if it is located in an interlocked sec-
tion of the diagram.
Controlling Bit Status Section 4-7
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