ADDRESSING MODES
S3C80A5B
3-8
INDEXED ADDRESSING MODE (Continued)
Register File
OPERAND
Program Memory
or
Data Memory
Point to Working
Register Pair
(1 of 4)
LSB Selects
16-Bit
Address
Added to
Offset
RP0 or RP1
MSB Points to
RP0 or RP1
Selected
RP Points
to Start of
Working
Register
Block
dst/src
OPCODE
Program Memory
x
OFFSET
4 Bit Working
Register Address
Sample Instructions:
LDC
R4, #04H[RR2]
; The values in the program address (RR2 + 04H) are
loaded into register R4.
LDE
R4,#04H[RR2]
; Identical operation to LDC example, except that
external program memory is accessed.
Next 2 Bits
Register
Pair
Value used In
Instruction
8 Bits
16 Bits
16 Bits
+
~
~
NOTE:
LDE command is not available, because an external interface is not implemented for
the S3C80A5B.
Figure 3-8. Indexed Addressing to Program or Data Memory with Short Offset