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ADDRESSING MODES
DIRECT ADDRESS MODE (DA)
In Direct Address (DA) mode, the instruction provides the operand's 16-bit memory address. Jump (JP) and Call
(CALL) instructions use this addressing mode to specify the 16-bit destination address that is loaded into the PC
whenever a JP or CALL instruction is executed.
The LDC and LDE instructions can use Direct Address mode to specify the source or destination address for Load
operations to program memory (LDC) or to external data memory (LDE), if implemented.
Sample Instructions:
LDC
LDE
NOTE: LDE command is not available, because an external interface
3-10
Program or
Data Memory
Program Memory
Upper Address Byte
Lower Address Byte
dst/src
OPCODE
R5,1234H
;
The values in the program address (1234H)
are loaded into register R5.
R5,1234H
;
Identical operation to LDC example, except that
external program memory is accessed.
is not implemented for the S3C80A5B.
Figure 3-10. Direct Addressing for Load Instructions
Memory
Address
Used
"0" or "1"
LSB Selects Program
Memory or Data Memory:
"0" = Program Memory
"1" = Data Memory
S3C80A5B
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