ADDRESSING MODES
S3C80A5B
3-6
INDIRECT REGISTER ADDRESSING MODE (Continued)
dst
OPCODE
4-bit Working
Register Address
Sample Instructions:
LDC
R5,@RR6
; Program memory access
LDE
R3,@RR14
; External data memory access
LDE
@RR4, R8
; External data memory access
Program Memory
Register File
src
Value used in
Instruction
OPERAND
Example Instruction
References either
Program Memory or
Data Memory
Program Memory
or
Data Memory
Next 2-bit Point
to Working Register
Pair
(1 of 4)
LSB Selects
Register
Pair
16-Bit
Address
Points to
Program
Memory or
Data
Memory
RP0 or RP1
MSB Points to
RP0 or RP1
Selected
RP Points
to Start of
Working
Register
Block
NOTE:
LDE command is not available, because an external interface is not implemented for
the S3C80A5B
Figure 3-6. Indirect Working Register Addressing to Program or Data Memory