4/17/98 6-5 Addressing Modes and Data Types
6.2.4 Direct Addressing
Instructions using this addressing mode contain an 10-bit address field, which contains the actual
address of the operand in any 64K data memory segment or sfr space.The direct address data
memory space is always the bottom 1K byte (0:3FFh) of any segment. The associated data
segment is always identified by the 8-bit contents of DS.
Example: SUB R0, 200h Before: R0 contains A5FFh
If DS = 02, the 200H contains 5555h
operand is in segment
2 of data memory.
After: R0 contains 50AAh
200h contains 5555h
Figure 6.4
ALU
SUB R0, 200h
0h
DATA MEMORY
REGISTER - DIRECT
REGISTER FILE
DESTINATION
FFFFh
DS = 2h
Seg2
200h
5555h
A5FFh
SOURCE
50AAh (result)
R0
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