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S3F80JB ADDRESSING MODES
3-9
INDEXED ADDRESSING MODE (Continued)
Register File
OPERAND
Program Memory
or
Data Memory
Point to Working
Register Pair
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, #1000H[RR2] ; The values in the program address (RR2 + 1000H)
are loaded into register R4.
LDE R4,#1000H[RR2] ; Identical operation to LDC example, except that
external data memory is accessed.
NEXT 2 BITS
Register
Pair
Value used in
Instruction
16-Bit
16-Bit
16-Bit
dst/src
OPCODE
Program Memory
x
OFFSET
4-bit Working
Register Address
OFFSET
+
NOTE:
LDE command is not available, because an external interface is not implemented
for the S3F80JB.
~~
Figure 3-9. Indexed Addressing to Program or Data Memory