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APPENDIX
●
Bit direct addressing
Bit direct addressing is indicated by dir:b in the instruction list. This addressing is used to access a
particular bit in the area between 0000
H
and 00FF
H
. In this addressing mode, the higher byte of the address
is 00
H
and the lower byte is specified by the operand. The bit position at the address is specified by the
lower three bits of the operation code.
Figure B.2-3 "Example of bit direct addressing" shows an example.
Figure B.2-3 Example of bit direct addressing
●
Index addressing
Index addressing is indicated by @IX+off in the instruction list. This addressing is used to access the entire
64-KB area. In this addressing mode, the address is the value resulting from sign-extending the contents of
the first operand and adding them to IX (index register). Figure B.2-4 "Example of index addressing"
shows an example.
Figure B.2-4 Example of index addressing
●
Pointer addressing
Pointer addressing is indicated by @EP in the instruction list. This addressing is used to access the entire
64-KB area. In this addressing mode, the address is contained in EP (extra pointer). Figure B.2-5 "Example
of pointer addressing" shows an example.
Figure B.2-5 Example of pointer addressing
SETB 34H : 2
XXXXX 1X
X
B
0 0 3 4
H
7 6 5 4 3 2 1 0
2 7 F F
H
MOVW A, @IX+5 AH
1 2 3 4
H
A
1 2
H
3 4
H
2 8 0 0
H
2 7 A 5
H
IX
2 7 A 5
H
MOVW A, @EP
1 2 3 4
H
A
1 2
H
3 4
H
2 7 A 6
H
2 7 A 5
H
EP