Samsung P8245 Microscope & Magnifier User Manual


 
S3C8245/P8245/C8249/P8249 INSTRUCTION SET
6-55
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