Samsung S3F80JB manual Direct Address Mode DA, Direct Addressing for Load Instructions

Models: S3F80JB

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ADDRESSING MODES

S3F80JB

 

 

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.

Program or

Data Memory

 

 

 

 

 

 

Memory

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Program Memory

 

 

 

 

Address

 

 

 

 

Used

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Upper Address Byte

 

 

 

 

 

 

Lower Address Byte

 

 

 

 

 

LSB Selects Program

dst/src

"0" or "1"

 

 

 

 

 

 

 

 

 

 

Memory or Data Memory:

 

 

 

 

 

OPCODE

 

 

 

 

 

 

 

 

 

 

"0" = Program Memory

 

 

 

 

 

 

 

"1" = Data Memory

Sample Instructions:

 

LDC

R5,1234H

; The values in the program address (1234H)

 

 

are loaded into register R5.

LDE

R5,1234H

; Identical operation to LDC example, except

 

 

that external data memory is accessed.

NOTE:

LDE command is not

available, because an external interface is not

implemented for the S3F80JB.

Figure 3-10. Direct Addressing for Load Instructions

3-10

Page 63
Image 63
Samsung S3F80JB manual Direct Address Mode DA, Direct Addressing for Load Instructions