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APPENDIX B Overview of the Instructions
● Bit Direct Addressing
The addressing, which is indicated by dir:b in the instructions list, is used for accessing the area from
0000
H
to 00FF
H
on a per bit basis. In this addressing, the higher one byte of the address is 00
H
. Specify the
lower one byte with the operand; and the bit position in the specified address with the lower three bits of
the operation code.
Figure B.1-3 shows an example.
Figure B.1-3 Example of Bit Direct Addressing
● Index addressing
The addressing, which is indicated by @IX(off in the instructions list, is used for accessing the entire area
of 64 KB. In this addressing, the contents of the first operand are signed and added to IX (index register).
Then the results are used as the address.
Figure B.1-4 shows an example.
Figure B.1-4 Example of Index Addressing
● Pointer Addressing
The addressing, which is indicated by @EP in the instructions list, is used for accessing the entire area of
64 KB. In this addressing, the contents of EP (extra pointer) are used as the address.
Figure B.1-5 shows an example.
Figure B.1-5 Example of Pointer Addressing
SETB 34H : 2
0 0 3 4
H
7 6 5 4 3 2 1 0
X X X X X 1 X X
B
A
IX
MOVW A, @IX+5 AH
2 7 A 5
H 2 7 F FH
1 2H
2 8 0 0H
3 4H
1 2 3 4H
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