Samsung S3C9228/P9228, 8-Bit CMOS Microcontroller user manual Direct Address Mode DA

ADDRESSING MODES S3C9228/P9228

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

Program Memory

Upper Address Byte

Lower Address Byte

dst/src "0" or "1"

OPCODE

Sample Instructions:

Memory

Address

Used

LSB Selects Program Memory or Data Memory: "0" = Program Memory "1" = Data Memory

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 program memory is accessed.

Figure 3-10. Direct Addressing for Load Instructions

3-10