Motorola 24-Bit Digital Signal Processor manual Load Updated Address, Operation Assembler Syntax

INSTRUCTION DESCRIPTIONS

	LUA	Load Updated Address	LUA
Operation:		Assembler Syntax:
	ea➞d	LUA ea,D

Description: Load the updated address into the destination address register D. The source address register and the update mode used to compute the updated address are specified by the effective address (ea). Note that the source address register speci-

fied in the effective address is not updated. All update addressing modes may be

used.

Note: This instruction is considered to be a move-type instruction. Due to instruction pipelining, if an AGU register (Mn, Nn, or Rn) is directly changed with this instruction, the new contents may not be available for use until the second following instruction. See the restrictions discussed in A.9.6 - R, N, and M Register Restrictions on page A-310.

Example:

:

LUA (R0)+N0,R1

:

Before Execution

R0 $0003

;update R1 using (R0)+N0

After Execution

R0 $0003

N0

$0005

N0

$0005

M0

$FFFF

M0

$FFFF

R1

$0004

R1

$0008

Explanation of Example: Prior to execution, the 16-bit address register R0 contains the value $0003, the 16-bit address register N0 contains the value $0005, and the 16-bit address register R1 contains the value $0004. The execution of the LUA (R0)+N0,R1 instruction adds the contents of the R0 register to the contents of the N0 register and stores the resulting updated address in the R1 address register. Normally N0 would be added to R0 and deposited in R0. However, for an LUA instruction, the contents of both the R0 and N0 address registers are not affected.

A - 148 INSTRUCTION SET DETAILS MOTOROLA