Immediate Addressing
Immediate Addressing
Immediate Addressing
Immediate Addressing
–
–
“#”
“#”
Fixed value part of program memory
Fixed value part of program memory
instruction
instruction
Supports short (8
Supports short (8
-
-
bit) and long (16
bit) and long (16
-
-
bit)
bit)
immediate constants
immediate constants
Long immediate can include a shift
Long immediate can include a shift
Used to initialize registers, and operate
Used to initialize registers, and operate
with constants
with constants
OPCODE
OPCODE
8
8
-
-
bit OPERAND
bit OPERAND
one word instruction
one word instruction
OPCODE
OPCODE
16
16
-
-
bit OPERAND
bit OPERAND
two word instruction
two word instruction
Immediate addressing allows the user to specify a constant within an instruction mnemonic. Short
immediate are single word, and execute in a single cycle. Long (16-bit) immediate allow full
sized values, which become two-word instructions - yet execute in a single instruction cycle.
Immediate Addressing
Immediate Addressing
–
–
Example
Example
Long Immediate, 2 Words (AND)
Long Immediate, 2 Words (AND)
loc16
loc16
#16Bit
#16Bit
AND
AND
AND
AND
loc16,#16Bit
loc16,#16Bit
Ax
Ax
#16Bit
#16Bit
loc16
loc16
AND
AND
AND
AND
Ax,loc16,#16Bit
Ax,loc16,#16Bit
ACC
ACC
#16Bit
#16Bit
shift
shift
AND
AND
AND
AND
ACC,#16Bit,<<0
ACC,#16Bit,<<0
-
-
16
16
Short Immediate, 1 Word (ANDB)
Short Immediate, 1 Word (ANDB)
AND
AND
automatically replaced by
automatically replaced by
ANDB
ANDB
if IMM value is 8 bits or less
if IMM value is 8 bits or less
ANDB
ANDB
ANDB
ANDB
Ax,#8Bit
Ax,#8Bit
Ax
Ax
#8Bit
#8Bit
C28x - Appendix B - Addressing Modes B - 7
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