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APPENDIX
● I/O direct bit addressing (io:bp)
Specify bits in physical addresses 000000
where the larger number indicates the most significant bit (MSB) and the lower number indicates the least
significant bit (LSB).
SETB i : 0C1
Before execution
After execution
● Abbreviated direct bit addressing (dir:bp)
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). Bit positions are indicated by ":bp", where the larger number indicates the most significant bit
(MSB) and the lower number indicates the least significant bit (LSB).
Figure D.3-9 Example of Abbreviated Direct Bit Addressing (dir:bp)
SETB S : 10
Before execution
After execution
● Direct bit addressing (addr16:bp)
Specify arbitrary bits in 64 kilobytes explicitly. Address bits 16 to 23 are specified by the data bank register
(DTB). Bit positions are indicated by ":bp", where the larger number indicates the most significant bit
(MSB) and the lower number indicates the least significant bit (LSB).
SETB 2222
Before execution
After execution
598
Figure D.3-8 Example of I/O Direct Bit Addressing (io:bp)
: 0 (This instruction sets bits by I/O direct bit addressing.)
H
: 0 (This instruction sets bits by abbreviated direct bit addressing.)
H
DTB 5 5
DTB 5 5
Figure D.3-10 Example of Direct Bit Addressing (addr16:bp)
: 0 (This instruction sets bits by direct bit addressing.)
H
DTB 5 5
DTB 5 5
to 0000FF
explicitly. Bit positions are indicated by ":bp",
H
H
Memory space
0000C1
0 0
H
Memory space
0000C1
0 1
H
DPR 6 6
556610
DPR 6 6
556610
552222
552222
Memory space
0 0
H
Memory space
0 1
H
Memory space
0 0
H
Memory space
0 1
H
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