Ldcd/Lded Load Memory And Decrement - Samsung S3C80A5B User Manual

INSTRUCTION SET
LDCD/LDED
LDCD/LDED dst,src
dst ← src
Operation:
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:
opc
Examples: Given: R6 = 10H, R7 = 33H, R8 = 12H, program memory location 1033H = 0CDH, and
external data memory location 1033H = 0DDH:
LDCD
LDED
6-54
— Load Memory and Decrement
dst | src
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)
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
Bytes Cycles Opcode
2 10
S3C80A5B
Addr Mode
(Hex) dst src
E2 r Irr