Difference between revisions of "LD (8-bit)"

Latest revision as of 07:30, 25 May 2012

8-bit Register Load

This instructions move the contents of a register or memory location into a destination register or memory location. These commands do not affect any CPU flags, and they require 1 machine cycle to complete (Plus 1 machine cycle if (HL) is used as a source or destination).

The op-codes for this group are encoded as follows:

 01dddsss
   | || |
   | |+-+- Source Register
   +-+---- Destination Register
 
 Where 'd' and 's' are values from the following:
 
 000: B
 001: C
 010: D
 011: E
 100: H
 101: L
 110: (HL)
 111: A

Example: LD B,L would be encoded as 01000101 represented in hexadecimal as $45.

NOTE: LD (HL),(HL) does not exist, that instruction ($76) executes the HALT instruction.

8-bit Immediate Load

These instructions allow a constant value to be loaded from the program into a register of choice. These commands do not affect any CPU flags, and they require 2 machine cycles to complete.

 00ddd110 nnnnnnnn
   | |    |      |
   | |    +------+- Operand
   +-+------------- Destination Register
 
 Where 'n' is the 8-bit immediate, and 'd' is a value from the following:
 
 000: B
 001: C
 010: D
 011: E
 100: H
 101: L
 110: (HL)
 111: A

Example: LD H, $A6 would be encoded as 00100110 10100110 represented in hexadecimal as $26 $A6