Samsung KS57C2308 Manual page 142

SAM47 INSTRUCTION SET
LDD
— Load Data Memory and Decrement
LDD dst
Operation: Operand
A,@HL
Description: The contents of a data memory location are loaded into the accumulator, and the contents of the
register L are decreased by one. If a "borrow" occurs (e.g., if the resulting value in register L is
0FH), the next instruction is skipped. The contents of data memory and the carry flag value are
not affected.
Operand
A,@HL
Example: In this example, assume that register pair HL contains 20H and internal RAM location 20H
contains the value 0FH:
LD
LDD
PS
PS
he instruction "JPS XXX" is skipped since a "borrow" occurred after the "LDD A,@HL" and
instruction "JPS YYY" is executed.
5-68
Operation Summary
Load indirect data memory contents to A; decrement
register L contents and skip on borrow
Binary Code
1 0 0
HL,#20H
A,@HL
XXX
YYY
0 1 0 1 1
; A (HL) and L
; Skip
; H 2H and L
KS57C2308/P2308/C2316/P2316
Bytes
1
Operation Notation
A (HL), then L
skip if L = 0FH
L–1
0FH
Cycles
2 + S
L–1;