Load Memory With Pre-Decrement - Samsung S3C80A5B User Manual

INSTRUCTION SET
LDCPD/LDEPD
LDCPD/
LDEPD dst,src
rr ← rr – 1
Operation:
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
Examples: Given: R0 = 77H, R6 = 30H, and R7 = 00H:
LDCPD
LDEPD
6-56

— Load Memory with Pre-Decrement

src | dst
; (RR6 ← RR6 – 1)
@RR6,R0
; 77H (contents of R0) is loaded into program memory location
; 2FFFH (3000H – 1H)
; R0 = 77H, R6 = 2FH, R7 = 0FFH
; (RR6 ← RR6 – 1)
@RR6,R0
; 77H (contents of R0) is loaded into external data memory
; location 2FFFH (3000H – 1H)
; R0 = 77H, R6 = 2FH, R7 = 0FFH
Bytes Cycles Opcode
2 14
S3C80A5B
Addr Mode
(Hex) dst src
F2 Irr r