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INSTRUCTION SET S3C8275X/F8275X/C8278X/F8278X/C8274X/F8274X
6-54
LDCD/LDED — Load Memory and Decrement
LDCD/LDED dst,src
Operation: dst ← src
rr ← rr – 1
These instructions are used for user stacks or block transfers of data from program or data
memory to the register file. The address of the memory location is specified by a working register
pair. The contents of the source location are loaded into the destination location. The memory
address is then decremented. The contents of the source are unaffected.
LDCD references program memory and LDED references external data memory. The assembler
makes 'Irr' an even number for program memory and an odd number for data memory.
Flags: No flags are affected.
Format:
Bytes Cycles Opcode
(Hex)
Addr Mode
dst
src
opc dst | src 2 10 E2 r Irr
Examples: Given: R6 = 10H, R7 = 33H, R8 = 12H, program memory location 1033H = 0CDH, and external
data memory location 1033H = 0DDH:
LDCD R8,@RR6 ; 0CDH (contents of program memory location 1033H) is loaded
; into R8 and RR6 is decremented by one
; R8 = 0CDH, R6 = 10H, R7 = 32H (RR6 ← RR6 – 1)
LDED R8,@RR6 ; 0DDH (contents of data memory location 1033H) is loaded
; into R8 and RR6 is decremented by one (RR6 ← RR6 – 1)
; R8 = 0DDH, R6 = 10H, R7 = 32H