S3F84B8_UM_REV 1.00
3 ADDRESSING MODES
3-8
3.8 INDEXED (X) 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
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
dst/src
OPCODE
Program Memory
x
OFFSET
4-bit Working
Register Address
+
~
~
Figure 3-8 Indexed Addressing to Program or Data Memory with Short Offset