INSTRUCTION SET

S3F80JB

 

 

LDCPD/LDEPD — Load Memory with Pre-Decrement

LDCPD/

LDEPD dst,src

Operation: rr rr – 1

dst src

These instructions are used for block transfers of data from program or data memory from the register file. The address of the memory location is specified by a working register pair and is first decremented. The contents of the source location are then loaded into the destination location. The contents of the source are unaffected.

LDCPD refers to program memory and LDEPD refers to external data memory. The assembler makes 'Irr' an even number for program memory and an odd number for external data memory.

Flags: No flags are affected.

Format:

opc

src dst

Bytes

Cycles

Opcode

Addr Mode

 

 

(Hex)

dst

src

2

14

F2

Irr

r

Examples: Given: R0 = 77H, R6 = 30H, and R7 = 00H:

LDCPD

@RR6,R0

;

(RR6 RR6 – 1)

 

 

; 77H (contents of R0) is loaded into program memory location

 

 

; 2FFFH (3000H – 1H)

 

 

;

R0 = 77H, R6 = 2FH, R7 = 0FFH

LDEPD

@RR6,R0

;

(RR6 RR6 – 1)

 

 

; 77H (contents of R0) is loaded into external data memory

 

 

; location 2FFFH (3000H – 1H)

 

 

;

R0 = 77H, R6 = 2FH, R7 = 0FFH

6-56

Page 184
Image 184
Samsung S3F80JB manual LDCPD/LDEPD Load Memory with Pre-Decrement, Ldcpd, Operation rr ← rr