127
5-7-2 DIFFERENTIATE UP/DOWN: DIFU(013) and DIFD(014)
DIFFERENTIATE UP: DIFU(013)
(013)
DIFU B
B: Bit CIO, G, A
Operand Data AreaLadder Symbol
Variations
!DIFU(013)
DIFFERENTIATE DOWN: DIFD(014)
(014)
DIFD B
B: Bit CIO, G, A
Operand Data AreaLadder Symbol
Variations
!DIFD(014)
Description DIFU(013) and DIFD(014) are used to turn the designated bit ON for one cycle
only.
Whenever executed, DIFU(013) compares its current execution with the pre-
vious execution condition. If the previous execution condition was OFF and the
current one is ON, DIFU(013) will turn ON the designated bit. If the previous
execution condition was ON and the current execution condition is either ON or
OFF, DIFU(013) will either turn the designated bit OFF or leave it OFF (i.e., if the
designated bit is already OFF). The designated bit will thus never be ON for long-
er than one cycle, assuming it is executed each cycle (see
Precautions
, below).
Whenever executed, DIFD(014) compares its current execution with the pre-
vious execution condition. If the previous execution condition is ON and the cur-
rent one is OFF, DIFD(014) will turn ON the designated bit. If the previous execu-
tion condition was OFF and the current execution condition is either ON or OFF,
DIFD(014) will either turn the designated bit OFF or leave it OFF. The desig-
nated bit will thus never be ON for longer than one cycle, assuming it is executed
each cycle (see
Precautions
, below).
These instructions are used when differentiated instructions (i.e., those prefixed
with a j or i,) are not available and single-cycle execution of a particular instruc-
tion is desired. They can also be used with non-differentiated forms of instruc-
tions that have differentiated forms when their use will simplify programming.
Examples of these are shown below.
Precautions Any output bit is generally used in only one instruction that controls its status.
DIFU(013) and DIFD(014), operation can be uncertain when the instructions are
programmed between IL and ILC, between JMP and JME, or in subroutines. Re-
fer to
5-8 INTERLOCK and INTERLOCK CLEAR: IL(002) and ILC(003), 5-9
JUMP and JUMP END: JMP(004) and JME(005)
, and
5-30 Subroutines
and
5-31 Interrupt Control
for details.
Note: Refer to page 115 for general precautions on operand data areas.
Flags There are no flags affected by these instructions.
Bit Control Instructions Section 5-7
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