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UM018809-0611 LD Instruction

ZNEO

CPU Core

User Manual

115

Definition

Load

Syntax

LD dst, src

Operation

dst

 src

Description

The contents of the source operand are loaded into the destination operand. The contents of the

source operand are unaffected. The default data size is 32 bits. Byte (8-bit) or Word (16-bit) data

size can usually be selected by adding a .B or .W, suffix, respectively, to the LD mnemonic.

When a 32-bit value is loaded into an 8- or 16-bit memory location, the value is truncated to fit

the destination size.

When an 8- or 16-bit value is loaded into a larger location, it must be extended to fill all the des-

tination bits. A “U” in the mnemonic suffix selects zero (unsigned) extension. An “S” in the mne-

monic suffix selects signed extension. An immediate source operand is always sign extended.

A “--” prefix in a register-indirect operand indicates that the address register is decremented

before the operation. A “++” suffix indicates that the address register is incremented after the

operation. Register predecrement and postincrement do not affect flags. See EXT for instructions

to load register values with extension.

See LEA for synonyms to LD opcodes that are useful for loading an effective address.

See PUSH and POP for instructions that store and retrieve stack data.

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Zilog Z16F2810 Manual do Utilizador Página 131