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APPENDIX
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Abbreviated direct addressing (dir)
Specify the eight low-order bits of a memory address explicitly in an operand. Address bits 8 to 15 are
specified by the direct page register (DPR). Address bits 16 to 23 are specified by the data bank register
(DTB).
MOV S : 20H, A (This instruction writes the contents of the eight low-order bits of A in
Before execution
After execution
●
Direct addressing (addr16)
Specify the 16 low-order bits of a memory address explicitly in an operand. Address bits 16 to 23 are
specified by the data bank register (DTB). A prefix instruction for access space addressing is invalid for
this mode of addressing.
MOVW A, 3B20H (This instruction reads data by direct addressing and stores it in A.)
Before execution
After execution
642
Figure B.3-6 Example of Abbreviated Direct Addressing (dir)
abbreviated direct addressing mode.)
A 4 4 5 5
DPR 6 6
A 4 4 5 5
DPR 6 6
Figure B.3-7 Example of Direct Addressing (addr16)
A 2 0 2 0 A A B B
A A A B B 0 1 2 3
1 2 1 2
DTB 7 7
776620
H
1 2 1 2
DTB 7 7
776620
H
DTB 5 5
DTB 5 5
Memory space
? ?
Memory space
1 2
Memory space
553B21
0 1
H
553B20
2 3
H
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