Samsung S3F80JB manual LDCD/LDED Load Memory and Decrement, LDCD/LDED dst,src Operation dst ← src

Models: S3F80JB

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INSTRUCTION SET

S3F80JB

 

 

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:

opc

dst src

Bytes

Cycles

Opcode

Addr Mode

 

 

(Hex)

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

6-54

Page 182
Image 182
Samsung S3F80JB manual LDCD/LDED Load Memory and Decrement, LDCD/LDED dst,src Operation dst ← src